Hmmnnn. If you REALLY TRUELY Trust her and she seems like a person who wouldn't spread secrets and rumors around, start a conversation about things you've never told anyone about. (i.e. - Favorite Dead Relatives, Goals in life that other people would think is farfetched, etc.)
If not (Or afterwards), start making dirty jokes. (Nothing too offending. Play a game of "What's Under My Kilt")
GAME
- This is a game where you think up off objects that SOUNDS dirty, but would be an every day object.
"What's long and firm, but can get squishy if you squeeze it too hard."
"A Banana! Ahahah! You thought it was a P---s!"
"It's bushy, you can pet it, and it'll twitch if you yank at it."
"A Kitty! Ahahahah!"
Etc. It's a fun game. Makes people laugh.
"Elevator doors don't like me. Automatic doors don't like me. Car doors don't like me. Closet doors don't like me. Hell, all doors don't like me... I'm so disfunctional."