But by the time he'd gotten back up and climbed up onto the chair, her mask was back on and her horn had flashed. Everything about her was controlled once again, carefully bottled up inside her. Always trying to look perfect in front of everpony, even herself. Her magic had fixed everything her shout had broken within the castle, and it was like nothing had ever happened.
"But I can change her, Spike," Twilight insisted. "I saw everything you saw that day. And I saw what she's capable of back at her town. ...What was that place called, again?"
"Those creepy singing brainwashed ponies you told me about called it Our Town, right?" Spike wondered. "Let's call it Her Town. Since she was the one in charge, and everypony belonged to her in mind and body."
"I saw that town of hers, I saw what she did to the timeline, and I know what she's capable of. If I keep her around, under my direct supervision, I can keep an eye on her and fix anything she does wrong."
"Except when you're not around," Spike noted. "Then she can brainwash anypony she wants until you get back."
"What else am I supposed to do?" Real emotion, Spike realized, she was showing it again. "Turn her to stone?"
"Can't you do to her what you did to Nightmare Moon, rainbow-blasting her into a tiny crying pony sorry for everything she did?"
"I wish," She sighed. "That only worked because Darkness corrupted her. The real Princess Luna was sorry for everything the darkness tempted her into doing. That little Alicorn who hugged Celestia and apologized for everything, shrunken by her feelings of helplessness, that was the real her. All Harmony had to do was chase darkness away to reveal that. If I did that to Glimmer-"
She stopped herself, unwilling to finish that sentence.
"She wouldn't change, would she?" Spike asked sadly. "Harmony can't reveal her true form. It's already out there, for everypony but you to see. Darkness doesn't tempt her into doing bad things, she just doesn't care if what she wants to do in the moment is bad for anyone besides herself and what she wants. Chase away the darkness in Glimmer, and there wouldn't be anything left."
Twilight had nothing to say.
Spike, however, had thought of something. "I still think that in one of those time-travel jumps she forced you on, you should have teleported us over to Glimmer as a filly. Then you could teleport us again and give her to Celestia, so she could get her to be with her little boyfriend, or maybe even end up one of her students just like you."
"No, Spike! That just wouldn't be right!"
"Why not? You'd give Glimmer something happy to replace her lost friend, so she could grow up happy!" Spike insisted, and muttered to himself, "Instead of never growing up at all."
"I can't do that!" Twilight insisted. "I'd be destroying who Glimmer turned out to be!"
"Is that such a bad thing?" Spike wondered.
"Yes!" Twilight yelled. "Yes, it is! What's gotten into you?"
"What's gotten into you? Did you wonder whether it was right to turn Nightmare Moon back into Princess Luna before you did it?"
"Yes, and I decided it was the right thing to do! I'm not just one pony any more, Spike, I'm a Princess of Equestria! I have to set a good example for Equestria. If I compromise on my ideals now, when do I stop?"
"When there are no more Glimmers left! Or Sombras, or Nightmare Moons, or Tireks, or any other kind of monster!" Spike yelled. "Come on, Twilight, do your job and be a Princess!"
Tears welled in her eyes and her body was shaken by heavy sobs. Thick wet tears fell from her eyes as the walls came crashing down. "I never wanted to be a Princess!" She screamed, and though she wished she could take that scream back, it was too late. The crystal cracks were set in stone. Castle shook and rocks started to fall, and Twilight leapt to Spike and formed a magical shell shield around him to protect herself and her closest friend. The walls of this crystal castle came crashing down around them until all was dust and sparkly rubble around the pair.
Spike felt his rage melt away, and his own tears welled in his own eyes. "Twilight, I'm sorry... It's all my fault!"
She wanted to run away. The sight of the devastation she'd accidentally caused horrified her. She wanted to curl up somewhere and cry and cry until she felt better. But she didn't. She stopped, closed her eyes, and blinked her tears away as she forced herself to calm down. She wasn't going to go to pieces now, not in front of Spike. She couldn't completely give in to her own feelings, not yet, not when she was this powerful. She couldn't trust herself to feel. "No, Spike. It's my fault. I broke the castle. Don't blame yourself for what others did."
Spike began to tear up again, unable to say what was on his mind.
When her pounding heart slowed and she trusted herself to speak, she spoke. "I never asked for this. I've never told anyone this, but I loved Ponyville. I loved how genuine and honest everypony is here, compared to how things were back home. I loved being treated like a regular nerdy pony amongst regular ponies, but that's gone now. I wanted to make Princess Celestia and all my other teachers proud. I wanted to be a good student, not..." She looked back at her own wings, which stretched themselves out. "This."
Spike began to tear up. "I didn't mean to make you cry-"