Everypony else is worried about Twi, Rainbow be like, "Any chance to watch dat flank in motion."

And she's not shy about it either.

"I just traded my lifelong friend into slavery for a book, you sure you want to resist?"

Suggestive horn placement is suggestive.

Rainbow's response upon getting a book as a present. Are we sure Twilight's not dreaming this?

Canon TwiDash