Rule #3--deal in reality. You know what really happened--don't let that get obscured. Don't act like there is another reality don't believe that their is another reality--you didn't do anything--period. There is no reason to compromise on the truth.
I liked Deborah's thoughts above--but don't pull the trigger too early--a fair fight is fun but an ambush rocks!
cool, calm, and unconcerned---
certainly the Girl Scouts have some type of honr code--request a hearing on the girls honor violation----put your focus on her first, mother second. If you have to worry at all. But I would prepare the psychological battlefield with comments like "Oh gee Marge, can you believe that someone would think I would touch one of their children---how odd. Too bad she isn't involved with her daughters activities--" or "Well, at least she was sober" (hee hee one of my favorites-----
bottom line, only you can make you feel bad----doesn't seem like you ought to here