An interesting question, one that I'm surprised hasn't brought about a million responses. This topic is asked frequently and creates a lot of stress in my kids. We all know that rape becomes rape when one of the people says no. Yet with little kids, things are often different. Boys and boys, girls and girls, and boys and girls play house, play doctor, play assorted make believe games. What was innocent exploration, fun, non-threatening behavior often gets twisted when an adult finds out and reacts or over reacts. If you don't feel harmed by the actions, then it was just part of growing up. If you were harmed, was it by the act, or the actions of people after? Where I work, many of my kids grow up seeing p 0 r n, watching parents, brothers with girlfriends or sisters with boyfriends having sex. So witnessing sex is not uncommon. Not that it is ok, or even appropriate, but if someone from that environment was to play doctor with someone totally sheltered, then there may be some coercion involved.
Now, for being 11-12, extremely common for girls to explore each other. Again, not that it is ok, fine, appropriate, but that it is not uncommon. Seems that they are curious about development of the body, why some girls at that age resemble women, while others look like escapees from kindergarten. And...just my opinion, but it seems that the media has made it acceptable for girls to be curious with girls. Where actions between 2 girls is ok now, where 10-20 years ago, it wasn't (seeing girls kissing on tv, etc).
As long as you didn't feel pressured, harmed, wronged, violated, then you went through a phase of growing up. It is not unusual to look back at our actions and question "what the hell was I doing / thinking?" but don't put your adult mind and logic into that or you will get yourself upset...or worse..
I hope this is some help and makes sense.
I had the week from hell...and I'm unwinding with a bit of wine..so I may ramble....sorry if I do...and let me know..so I can redo it later..