Nah, she only cracks when Celestia's involved. She's not very good when she thinks she might do anything to disappoint her teacher. Shouldn't be an issue.
I'd put AJ as my #2 choice though, and think she'd make a good VP or cabinet member/adviser for Twi. I'd just rather have the smart one in charge than the stubborn one with a history of not accepting help.
Zevox