I was being quite serious in my previous post.
Be the bookie.
Take her bets. Pay her if she wins.
At the end of the evening, in the unlikely event she's up, she can feel good treating YOU to dinner, with your money.
If she's 'down' - you're not. You can cheer her up by taking her to dinner.
Either way, you pay for dinner at the end of the evening which you were going to do anyway.
Two Tips:
#1. Don't blow your edge by betting yourself...
#2. Make sure she's not a hustler.