Barb took a step back, cheeks warmed. "Oh! Um..." She had stepped right in it. Veering around the topic felt impossible. Rarity had called her out! "Um... You are still... the prettiest pony I know..."
Rarity fanned herself lightly with a hoof. "Delighted to hear that, dear. But that hardly says your feelings about it."
"Right!" No escape... "I'm not sure there... is a next step... You're the prettiest thing I ever saw, and you still are."
Rarity considered Barb for a quiet moment. "I haven't... been fair."
Barb blinked at that. "What'd you do?"
"Nothing. Everything." Rarity turned away with a heavy sigh. "Poor thing. You have no idea what you feel, and that's about where you should be, isn't it, darling?"
Barb hurried forward to grab one of Rarity's hind legs, hugging firmly to her. "I know we're friends and I don't want that to stop."
Rarity put a hoof on her head, mussing her softer spines. "You are too kind. Dear... Hm, as a little boy, it was easy enough to pass it off as a sort of puppy love. As a girl, this feels more awkward than usual, considering your amor hasn't changed at all. Little wonderful dragon, do you even know what you'd do if I said yes?"
"Um?" Barb slackly let Rarity step free. "Said yes to what? Oh! To being my special somepony?" Her cheeks light up a bright red. "Um! I'd... We'd go places, besides gem hunting." She rocked forwards and back on her feet, fingers dancing together. "Hang out by the pond? Watch a movie? I could make dinner! It'd be so much fun!"
Rarity's eyes welled with new tears. Evidence of how cruel she had been was being rubbed in her face, and ignoring it felt impossible to do any longer. "Darling... I would be delighted to do all of those things, but that makes us friends, not special someponies. And we are already that." She offered a hoof towards Barb. "A dear and beloved friend I care for so very deeply."
Barb took hold of Rarity's offered hoof. "But there's more! I'd be allowed to kiss you." She colored anew. "And you could kiss me. That's what special someponies do."
Rarity casually planted a smooch on Barb's cheek. "Darling, I have kissed you several times."
Barb thought back on that, almost woozy from the blushing she was doing. "Uh... yeah, you did."
"Well then, that can't be it." Rarity held up a hoof. "Dear, you are a little thing, still growing... I am an old mare. We can be friends, so very good friends, but special someponies? That is..." She swallowed thickly. "Improper... Yes, improper. You deserve somecreature closer to your age."
"You are not old!" hotly burst out Barb, her color shifting from embarrassment to anger almost instantly. "You're wonderful! And young! How could you say that?"
"Compared to you?" Her mascara began to run lightly with her thin tears. "Compared to you, dearest Sp--Barb, I may as well be ancient. Really... I will be well middle aged by the time you finish growing. That is the way of things." She grabbed Barb by the cheeks between two hooves. "That isn't to say I don't love you, because I do, and always have. You are one of my dearest friends, and I hope that continues, darling."
Barb felt her own tears rising to the stinging surface, sniffling noisily despite her efforts. "That isn't fair..."
"No... But there's not much for either of us to do about it, dear." She leaned in, touching nose to nose with her precious dragon. "You will grow up to be a stunning creature, this I know for sure. I will be proud to know you, and be your friend, but I can't be your plus one."
Barb sagged back, squirming in place. "S-so..."
"I will gladly make that dress for you, dear." Rarity waved aside at her collection of creations. "Without reservation."
"Yeah..." Barb's heart wasn't in it, not at that moment, but she went through the motions.
Twilight sat up sharply as a door slapped shut. "Who's there?" There were only a few creatures that'd wander in, and few of them would slam a door like that.
"It's me," came the sullen tones of Barb as she plodded into sight.
"Barb, welcome back." Twilight hopped free of her chair and hurried towards her assistant and sibling. Her trot slowed to a stop. "You look..."
"Rarity dumped me." Barb played with her fingers in a fidget. "We didn't even get together and she dumped me..."
Twilight cringed, ears pinning. She offered a hoof and soon had a shaking dragon against one of her arms. She drew Barb close, hugging them gently. "Sorry."
"Sorry? What'd you do?" Barb nestled with her despite that. "You didn't tell her to do that, right?"
Twilight set her free hoof on her face. "I should have, perhaps."
Barb frowned at the idea. "What? Why?"
Twilight booped Barb's nose gently. "It's complicated... but I was fairly certain you two would never... be a couple."
Barb sagged with defeat. "Because I'm too young?"
"That... but, perhaps more importantly." She spread her hooves in front of Barb. "You're in different parts of your lives. You're still discovering you. In fact, you're in the middle of that in a big way right now, Miss Barb. Rarity is an adult, with a business, several actually. You're far from the same level of maturity. That's not an insult. We were all at your stage before." She rubbed her fuzzy cheek. "I admit, mine included little consideration of what it'd be like to be a stallion, but trying to figure out my place as a mare certainly came up."
Barb poked Twilight dead center on her chest. "I was there to help. I remember that." She was smiling lopsidedly. "You were a mess."
Twilight burst into giggles. "I really was... Thank you for being there, even if it confused you, a lot. Which, right there, see? You were a great little brother, back then, but you didn't know what I was going through. You were just the best little sibling I could ask for..." She smiled brightly. "And I imagine Rarity sees the same thing now. You're a wonderful, treasured, and beloved friend, but not her partner. Partners stand eye to eye." She wobbled between her eyes and Barb's. "Which means they need to be closer, um, not physically, but maturity."
Twilight sat up. "And now it's my turn. You're learning what it's like to be a dragon mare, and I will be there, to help. I know what it means to be a mare, even if the dragon parts elude me... What I mean to say is that if you need anything, don't hesitate to ask. Me and Smolder." She wriggled her nose at Barb. "Lucky! You get two older sisters. I didn't have any of those."
Barb laughed, a choked sound as she wiped an arm across her face. "Thanks... It just hurts, you know? Um... I'm... glad we're still friends and all." She played with her fingers fretfully. "I still think she's pretty. Is that wrong?"
It was Twilight's turn to darken. "Um! She puts a lot of effort into her presentation. I... feel certain knowing it's working is very appealing to her."
"Just not as a special somecreature." Barb sighed and climbed up to her feet. "I get it..." A sly smile spread on her lips. "But she did tell me something I didn't know before."
Twilight perked at that. "What's that? You look excited by it, whatever it is."
Barb fired a thumbs up. "Rarity said that kissing is not a special somepony thing. Friends can kiss."
Twilight inclined her head. "This... is true. It's also a family thing. I've kissed you before."
Barb froze. Had she? She had! "Wow... how did I not realize that?" She went in and smooched Twilight right on the cheek. "It's a whole new age!"
Twilight laughed gently, accepting the kiss. "Are you going to go around kissing everycreature you like?"
"Maybe." Barb shoved her hands behind her back and rocked with a sly grin on her face. "Smolder deserves one for sure."
Twilight pushed a new book against Barb. "Then you should study this."
Barb accepted the book with a raised brow. "The Courtesies of the Formal Kiss? What is this?" She peered at the thick book.
"It's exactly what it looks like." Twilight nodded with confidence. "There are rules about how to kiss and be proper. A common way to kiss a friend who is not a special somepony is like this." And she kissed Barb on either cheek, hooves on Barb's shoulders. "If you go for a hug while you do it, that is a mark of greatly increased intimacy, reserved for very special friends you've had for many years." She pointed at the book. "Read."
Barb held the book balanced on one hand, the other scratching at a cheek. "Huh... I didn't know there were... fancy rules about it."
"You have no idea." Twilight waved at the book. "But you will."
Barb turned the book against herself, hugging it. "Thanks. I'll do that, promise. Um... Thanks! Really... I know this has to be so confusing. It's confusing to me too."
"But you like it." Twilight stood up. "You're smiling, a lot. Now... I can't claim I understand it entirely, but I do understand you."
"Um, do you?" Barb raised a scaled ridge with doubt clear on her face.
"As a sibling, yes." Twilight nodded with confidence. "And I can see you're happy. Confused, certainly, but happy... Happy in a way I never realized you weren't before. You've found something new and strange and wonderful and you're still figuring out how you... How you are... You're figuring out Barb, and that's a fine thing to figure out."
Barb couldn't see. Oh, she was shedding a few tears. She wiped them away hurriedly, clearing her face. "T-thanks! That means a lot. Wanna figure out Barb with me?"
"I would be honored." Twilight dipped her head. "I never had a little sister before, but maybe I always did. It just took us this long to notice the fact."
Barb caught on that. "Woah..."
"Is everything alright?" Twilight inclined her head at Barb. "Do you want some tea? It's been a long day."
"Um, maybe later." Barb waved that way. "I just never thought of it that way before... Wow... Maybe I was?"
"A filly? I thought that was what you were saying in the first place." Twilight rose to her hooves. "We're just making the outside match the inside and all that." Her wings fidgeted on her back as she headed towards the kitchen. "Sorry for not noticing earlier."
Barb trailed after her. "Well, I mean... I didn't notice either. You can't blame yourself for that... Um..." She squeezed the book about kissing. "I'm lucky to have a good sister."
"Even if I wanted to hold you back?" Twilight peeked over her shoulder. "I was very alarmed... I'm still a bit rattled, but I want what's best for you."
"I know that, really... We were all confused." Barb poked her on the rump. "Discord shouldn't have done that! That was mean of him."
"I thought you wanted him to change you? Why would that be--"
"--I mean changing you! Making you a stallion, even for a little while. That part was mean of him." Barb gusted out a sigh, tail twitching in thick sways. "Heavy handed."
"Heavy handed is one of his things." She reared up, horn glowing as she retrieved a box of tea and set it on the counter and got to filling a kettle with water. "To be honest, I'm more surprised you manage to deal with it with him as a player in your game. You must be very good at it."
Barb colored at that. "I do my best... I think he likes it, and I like having him there. We have a good time!" She snatched a tea bag and plopped it in a cup before Twilight could, only to do it with a second. "Let's both have some."