Actually, I wouldn't be to concerned. When I was 7 or 8. This is very embarrassing but my sister and I actually played around a little sexually. I thought It felt really good. So therefore she may just do it for pleasure. But I'm 17 now and I still get really sexually hyper and active.
Thank you. Boy touched her and she touched him. Going to therapy
Its normal for kids to be curious, but honestly a with seven year old being that hyper sexual I would be concerned that there may be more going on then just influences from neighborhood kids....I would want to talk with her about if she's ever been inappropriately touched by someone older. I think that taking her to a therapist is a good idea, and I'm sure your pediatrician would want to know as well.