Great story. Glad it worked out so well for you! However, you are replying to a very old post, so I doubt that your message was received.
Nothing may have happened. I got the same idea when I was about 6. The first two boys I approached wouldn't go along. The third one did. We were never caught and we continued to show and then to touch each other. This led to scat and, much later, full sexual activity. Our parents and friends must know that we're sexually active now, because we married two years ago. (Without ever dating anyone else!!!)
Coming from someone who was molested by a family member who was relation by marriage from ages 7-12 it's possible that something may have happen that she's afraid to tell. I didn't tell my family until I was 22!! The only time kids re-enact or even act out manners that wouldn't be normal for a child of that age to do things of that nature usually stems from it being done to them. I wish this upon no parent to have to go through but where else could a 7 year old child think to ask 'lets play a game' that involves pulling down of the pants and underware. You need to let her know in a very concerned yet gentle tone that if something has happened you will not blame her and it isn't her fault. If she proceeds to tell you nothing happened I would do some further investigating and seek out help from your pediatrician who can guide you in the steps to take next. Keep the incident and date and time documented for your records so that you can give it to the doctor/therapist.
I wish you both well ;))