Did my sister molest me, or just childhood curiousity?

I have a strange situation. My older sister (I'm male) is in a deep depression because she thinks (and my mom thinks) she molested me when we were little. I remember the situation and think it was not a big deal- weird, I know, that I'm the one trying to convince her that it's not a problem. Basically, we saw a movie in a hotel room (our parents were in the adjoining room and didn't know), and my sister acted out a scene from the with me. She was 11, and I was 5. I remember the incident well- all that happened was she "humped" me- there was no force, threatening, no touching each other's privates or kissing. I really remember it as a game. I know she is older, and I think that's why she feels so guilty. That and the fact that we were both in pajamas, so there was some, er, skin to skin contact (but no or attempted . ew). As an adult, she told me she had never seen of any type before that incident, and she thinks she was imitating what she saw. She didn't get anything ual out of it, and I believe her. She has never threatened me to not tell anyone, or that we have to keep it a secret. I think she was so young she didn't even think of it like that. I told her it's really not a big deal, and it only happened that one time. I truly believe in my heart she did it because she was curious, and had no intentions of hurting me. I also don't think she had any concept of what she was doing- I know when I was 11, I didn't understand what was the way I did later as a teen/adult. I think my mom is to blame because my sister admitted this to her, and my mom completely flipped out. She is calling my sister a child molester and that she should turn herself into the police. This situation was over 25 years ago! Did my sister really molest me, if she herself was a child and didn't even know what molestation was?