I don't think it was abuse because something could have been done, even if she, herself, did not feel emotionally able to at the time. I would consider her an adult at 18. I do not think anything was her "fault" though, I would neither think badly of myself for having had this happen to me nor for not being able to stop it at that time. I would be grateful I was not raped. I would use my response to indicate to myself what I needed to work on, probably best with a therapist.

I would figure out how to remove myself from the situation, get away from any type of relationship or even contact with this man. I would tell someone I trusted what had happened, a teacher or good friend, therapist, etc. so that I could share my fear, anger, confusion, etc. and didn't have to carry it all myself.

I would work very hard to realize it was something that happened to me and was not part of Me. It was an unpleasant event in my life, not a reflection of me or my character.