Did my sister molest me, or childhood curiousity?

My older sister (I'm male) is really depressed 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 4. I remember the incident- all that happened was she "humped" me- there was no force, threatening, no touching each other's privates or kissing. I know she feels guilty because it was her idea, she was the older one, and we lifted each other's pjs so there was skin to skin contact (but NO or attempted- ew.) As an adult, she told me she had never seen 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. She told me she knew she shouldn't do it, but did not realize what or WHY she shouldn't do it until she was in her teens, and that's when she began to feel really guilty. I told her it was a completely isolated incident, and I honestly doubt it would have even happened if she didn't see the . I think my mom is to partially to blame because my sister admitted this to her (hoping for reurance or to get it off her chest, I guess), 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? I feel she is a good person, has never been in trouble as a child or adult, and this is being blown way out of proportion.