"Please, Twilight," Luna pleaded. "You are a princess of Equestria now. Please call me Luna."
Twilight rolled the idea over in her mind. She wanted to comply, she really did, but after thinking about it, she decided that she couldn't. "I'm sorry Princess," she said, her ears drooping as she looked down at the ground. "I just... can't."
"But, why?" Luna asked, puzzled.
"Well..." Twilight paused, looking back up, but averting her eyes, and wondering how she was going to put it. "I know I'm a princess now, and I know we're supposed to be equals, but it just doesn't feel right. You know? I mean, you're the Princess of the Night, and I feel like I'm still just a glorified librarian with a horn and wings."
Luna cocked an eye at this, but Twilight was looking back at the ground again, so she didn't notice, and continued.
"You've got purpose. You raise the moon and control the night, you rule Equestria and have fought battles along side Princess Celestia, and you're far older and wiser than I