i had a similar situation with a best friend of mine and her sister. it started when i was maybe six or seven or so. it was either after or around the time i believe i was abused by a man who lived in our home for a few months.

with my friend, it was not that often but was definitely not normal. she was very manipulative and outgoing. everyone liked her, and for some reason i could not stop being friends with her. i finally stopped being friends with her when i was 15 or so and will have nothing to do with her now even if it's just through facebook. she also was sometimes abusive towards me in mild ways like pinching my legs if i was going up the stairs on the slide at school because i wasn't going fast enough, etc.

some of what happened with her and her sister was consensual and okay with me. i did other things with other kids of a sexual nature that was not harmful to me. but with her, it was different sometimes.

also during those few years, i had been abused by two others who were older than me (males) and had an incident with two boys (brothers) who were a year and two younger who told me if i didn't do what they said, their dad said i couldn't play with them anymore. it confused me because i did not want to do it, yet i didn't know how to get out of the situation. so, having had all that happen in my early childhood really affected me on top of living in a home with family violence from six or so years old until i was 11.

those types of experiences can affect you as you get older. even now, i still have specific issues with what happened with my friend and i that makes me feel really stupid.