The fact that one cannot remember picking its body does not change the fact that it is the most logical assessment as to how it came to be born.
As to WHY a soul would choose that mother, I have heard that there are a tremendous amount of souls who want a life on earth and there are very few bodies to go around, and so souls will pick bodies that have bad parents or bodies with genetic diseases because ANY lifespan is a better one than none at all. Seems reasonable to me.
As I said before, it is still the mother and the boyfriend's fault, since they are responsible for their own actions.
When Jodi Foster's character wore a short skirt and got drunk and flirty in the movie The Accused, it didn't excuse the men who raped her at the bar she was in.