Rarity's adaption back to Equestria - with Nightmare feeding her her own memories of the life she'd returned to in a controlled manner - went rather smoothly. While at first she had been concerned her new wings might have caused problems, she discovered that it was remarkably easy to avoid discussion - or even comment - regarding them. Much like her friend Twilight's new wings - and status as a Princess - outside of Ponyville few noticed or even commented on it unless it was brought up, and ponies in Ponyville apparently only noticed because they were present for the rather showy ascension. Rarity seeming to wake up one day with bat wings barely caught any eyes, especially since she didn't make a fuss about it. Given her apparent reputation as a drama queen, it was easy to understand the logic of "Rarity doesn't make a fuss=it's not important".
The real issue she came across was a discovery regarding Nightmare herself. Given the intense training Rarity had given herself to supplement her own less than vast magical reserves with whatever ambient magic was in her environment, the much higher ambient magical energy levels made some spells more difficult to handle, though she was able to adjust without too much trouble or attention, especially with Nightmare's coaching. The real headache was the discovery that Nightmare could use those higher levels of magical energy to reach beyond Rarity's body to influence her surroundings to a certain extent. However, they did come to an agreement that Nightmare would not do anything to cause anyone irreparable physical or mental harm, and make sure to cover her tracks...and stop flirting with Discord. He was so not Rarity's type.
The first major confrontation between Rarity and Nightmare in this regard had come during a trip Rarity took with her friends to Manehatten for fashion week. She had made a decision that - unless a revelation proved necessary - to keep her life as Batmare and Miss Wayne separate from her life as Rarity of Ponyville if at all possible. As such, she did her best to slip into her old life without notice - save the bedtime stories she told Sweetie Belle, who had Pinkie Promised not to tell anyone without permission - and even resurrect a few old behaviors. As such, although she didn't trust Suri Polomare when the mare had started cozying up to her before the show, she had decided to give her the benefit of the doubt, giving her a bolt of the special fabric she'd made for her own new line to experiment with back home.
Suri Polomare did not appear in time for the show, much to the upset of Prim Hemline, who was running the show. Rarity's line was exceptionally well received, and she had plenty of time before the show started to attend the attractions her friends planned to go to.
It was on returning from the first such attraction that the news was heard. Suri Polomare was found amidst a half finished clothing line of her own that - in this light - was a blatant copy of the line Rarity had presented, and hanging from the ceiling, hogtied in the remainder of the bolt of special fabric Rarity had given her.
You can't seriously be upset about me giving that copy-catting witch what was coming to her, Nightmare growled as Rarity withdrew for 'private meditation' before the show.
No, I'm not angry about what you did to her, Rarity thought back. I gave her one chance to be better than I expected, and she failed.
...Are you angry because I made sure she was found out?
No, that was quite well done.
Then what are you angry about?
The waste of fabric! We worked months on that cloth to make it so perfect and unique, and you tied her up in it! It's a criminal waste of good fashion!
How else was I supposed to make certain no one would ever believe you or your friends had done it? Nightmare countered. I am supposed to cover my tracks, after all.
Rarity mulled that over for a time. Touché, she finally admitted.
After the show, Rarity found herself approached by a young mare who seemed almost unnaturally shy and quiet...and Rarity knew Fluttershy, so that was saying something. "Umm...excuse me..." the blue maned mare said softly.
Rarity turned to her, her glasses - updated with Equestrian data as she gathered it - giving her the information she needed. "Miss Coco Pommel, was it?" Rarity asked.
"Yes. I was, well, Suri's assistant..." Her voice trailed off nervously.
Rarity thought for a bit as to how to handle this situation, then smiled gently. "And I imagine this recent revelation has put you out of work?" At Coco's nod, Rarity gestured to a nearby tea shop. "Why don't we talk about a few things, shall we?" she asked gently.
Coco followed easily...far too easily for Rarity's comfort. "What would you like to talk about, Miss Rarity?" she asked gently.
"Well, I looked over some of Suri's past fashion lines after that disastrous revelation," Rarity explained. "Knowing that she would do such a thing, I noticed that many of her lines showed traits of other designers whose lines I've seen. I wasn't her first attempt at this, was I?"
Mutely, Coco shook her head.
"However, I did notice some lines that did have a common...artistic hoofprint, if you will," Rarity explained. "Tell me, did you play a part in her...creative adaptions?"
Coco shook her head. "No. I just carried materials back and forth during that time." Her eyes widened. "I-I was out getting Suri her coffee when-"
Rarity waved her hoof. "Darling, I never dreamed of implying you had a hoof in that dreadful scene she was found in. Actually...what I had determined was that, if I'm not mistaken, all of Suri's more recent lines that weren't 'creative adaptions' were your work, which she took credit for."
Coco glanced away, not meeting Rarity's eyes.
Rarity smiled widely. "Now, you mentioned you were out of work? Am I to assume you are looking for a new occupation?"
Coco nodded. "A-and a new place to live." Her eyes refused to leave the table.
Rarity tilted her head in confusion. "You were...staying with Miss Polomare?"
Coco nodded again, her voice even fainter this time. "So I was...readily available...if she needed anything..."
Having grown up in Gotham and hearing a full history of scandal regarding the behavior of certain 'professionals' - especially in the fashion industry - Rarity's mind jumped to a conclusion she hoped was erroneous. However, she decided to take some action here. "Miss Pommel, the reason I bring this all up...is because I see that you have some real talent, talent I don't want to see squandered."
Coco's eyes perked up. "A-are you by chance looking for an assistant?" she asked desperately.
"I'm afraid not," Rarity replied. "That role is admirably filled already by a dear friend of mine." Seeing Coco's eyes start to fall, Rarity smiled. "However, all things considered...I have been looking for a junior partner."
Coco's eyes widened as she lifted her head, staring at Rarity in disbelief. "You're kidding!" she gasped quietly.
"Not at all," Rarity replied. "A mare of your talents can go far in the fashion industry with the right push...and my own focus on my life is based entirely in my hometown. Fashion, while a passion, will often be sidelined as a secondary concern. I will need someone to help me with my business, to cover for me when I'm called away on other matters...and to handle matters of the business focused elsewhere in Equestria. I think you would be ideal for such a position."
Coco looked intrigued but nervous. "T-that does sound wonderful...b-but where would I live? I...don't exactly have much in terms of savings. Suri...didn't pay well and...I had to pay for things she sent me for out of my own pocket..."
Rarity smiled. "Well, until you've made enough to get your own place wherever you choose to live, I do have a spare guest room in my home and Boutique back in Ponyville." She saw gratitude but hesitation in Coco's eyes, so she took a risk she hoped would be greeted with confusion. "It locks from the inside."
The relief that became visible in Coco's eyes made Rarity sick to her stomach, but she hid it valiantly. "Oh, Miss Rarity, I'd be happy to accept!" Coco's beaming smile gave her a gentle, angelic beauty that wasn't visible before when she looked so downtrodden. "I've been working so long for Suri, I didn't think it was possible to make it in this town without looking out only for yourself. I won't let you down!"
"I'm sure you won't," Rarity reassured her. "Now, do gather your stuff. My friends and I will be returning to Ponyville on the next train, and you wouldn't want to be late!"
As she watched the poor mare bounce happily away, Rarity's mind turned inward. Nightmare, about Suri...
Already on it, Nightmare hissed, rage plainly audible in her thoughts. How far will you allow here?
Rarity's rage was at least as strong as Nightmare's, though it showed not on her face. As she turned towards the train station, she stated her case in her mind. I will not allow her to die.
Much later, Rarity would find self doubt in the fact that she didn't find Nightmare's maniacal cackle disturbing...