They were in the Beautiful interior of one of the many rooms in the castle in the giant tree.
"So, then i began to cast the spell, right? Then, I know, rookie mistake, I hit her shades and it bounced back at me. So, now, I, erm, uhh. Yeah." Twilight did her very best to hide her smile, failing badly. "Oh come on! First Bon-Bon, now you too? What's so funny?!"
"Nothing, nothing, just, wow. I'll try to find a counter-spell, but you should really, uh, just, not. Really, next time you try a new spell, at least tell me so I can make sure it doesn't backfire. I do have a 1-way anti-magic bubble spell, you know." Twilight getting over it, unlike the candy vendor next to her. "Not as if I would use it on Bon-Bon though." This gave Lyra an idea.
"Bon-Bon, you think this is so funny right?"
"What are you doing?" She saw Lyra charging her horn, and internally panicked. "No, you wouldn't dare!"
"Relax, I wouldn't unless you asked for it enough. Not as if you would want me to, I suppose. Am I right?" Bon-Bon was no longer smiling, or anything along the line of it. Somewhere in Ponyville, Pinkie was breaking the 4th wall and saying "It is funny, though."
"It might be some time before I find a counter, and by then it might have worn off, so no guarantees." Lyra nodded, and was on her way back to the shop.
"So, I'm stuck like this for now."
"Yeah, I guess. You wanna- never mind. Not a good idea considering your situation." Wanna what? This made Lyra curious.
"Wanna what?" Lyra responded, hoping Bon-Bon wouldn't shift the interest.
"I was going to say go drinking, but, not a good idea." Lyra nodded, seeing how that would be anywhere from embarrassing, to very, very, very bad. They had just walked inside, and shut the door behind them. Once they did, they both went their separate ways. Bon-Bon to the desk of the shop, and Lyra down into the cellar. Lyra opened the book again, and flipped back to the page with the spell. There was no counter-spell in sight, not before, not after the spell. There was a knock, and a familiar voice. Starflight Stream. Her magic sparring buddy.
"Is Lyra here? We have a scheduled match today." Please Bon-Bon, do something!
"Well, funny story short, she cant go outside right now. Magic mishap." Lyra really hoped Starflight Stream would just let it go.
"Come on, it cant be that bad. and if it is, I can help."
"Really, just not today. Come on." Lyra really wanted to help, but no. There was already three mares who knew, she couldn't risk a fourth knowing.
"Let me in, at least to help her out. It cant be that bad, right?" She then heard the door swing open more.
"Wait! Let me call her at least. Lyra! Starflight's coming down! Get ready!" Lyra quickly opened her emergency wardrobe, in case she had to hide anything down there. She even had a sheet that could serve as a wall. She grabbed a decently large blanket and wrapped herself up in it. Seconds later, a black-coated unicorn with a beautifully contrasting purple mane in a shape similar to Vinyl's.
"What did you do to yourself this time? Cuts, burns, deformation, etc?"
"Erm, a mix of 3 and 4 i guess? It's kinda, um, awkward."
"Is it loss of magic, or what?" Lyra shook her head, and Starflight continued to guess. "Is it wings? No, you wouldn't be hiding like that. Maybe a cloak, but that's it. Could it be-" The unicorn blushed, then the biggest childish smile spread across her face. "Are you still a mare?" Lyra had a your-death-will-be-swift look carved in the unicorn's face.
"You too? Even you find this more funny that it is?" And with that, the (for certain) mare was rolling on the floor with absurdly loud laughter. Then, without warning, a beam launched at the laughing mare, only to be blocked by a null beam.
"Hey! Hey! You don't have to curse me with that! Keep your freaky-" And was drowned out by her own snickering. "Okay, okay. Let's try to fix this, alright? Did you even try yet?"
"Me and Twilight were both supposed to be studying on the spell, until you came along." Putting emphasis on the word both, and hoping her friend would take the hint.
"Wheres the book where you found the spell?" Lyra levitated to the book on her desk to Starflight. "Ah, right here. No counter-spell? That's, actually pretty weird. Normally, there is a counter to everything. You wanna just guess stuff? I have a reflect spell, as you know very well." Lyra once recalled in a sparring match when Starflight used said spell to reflect a confusion spell, instantly giving the match to her.
"Wow, your still proud of that match." Lyra focused on combining affects of different spells in her head, and compiled a weird mix of a changeling magic channel, illusion, matter sifting, and bits of some other exotic spells based on potions from the zebra Zecora's potions.
"Okay, use the mirror spell." The purple circle appeared, and Lyra cast her Frankenstein beam into, and it hit, and bounced back to Lyra. Once it hit the mint-green unicorn, nothing happened. "Nothing."
"Really? Try again, I guess." Starflight reused the mirror spell. Lyra knew this would never work, as it never did, but it was worth a try. She cast the same gender spell that had cursed her in the first place. It hit her, and backfired immensely, just like she thought it would. She turned into what would be the farthest from what she wanted. He was now a big, red, farm pony who never used his voice much outside the quartet.
"You use the same spell?" The newly earth pony nodded. "My turn, then." Starflight becan casting something, and it turned the red farm pony into a Lyra-sized changeling. "Should work for now, right?"