What's interesting to me is the set up. How would you go about that? Would you be there for a session, and unsuspectingly be tied up with no knowledge that she knows something about you sneaking around??
I think if you have answers to the questions she's asking it would make it that much more tempting to reveal the information you have to stop the tickling. Maybe have some evidence planted on you or in the room that would make you guilty as all hell??
Good luck with this, and it's nice to know that you and your GF get along in this way. Cheers!!