hug sasha - this has got to be really hard for u to know about. and hard to try to figure out what the best thing to do is. my eyes got watery thinking of how difficult this is for u and the girl. u have a lot of responsibility on u. i feel for u. really i do.
i have also had the same kind of bad experiences with basically every single institution i have had any thing to do with. so that puts even more responsibility on u. how nice it would be if we could just call someone else. but in my many years of experience now, that just hasnt happened. once when i reported something the lady who was taking the report actually started lecturing and judging me. and she never did anything with the info.
i work mostly with emotional abuse cases so those are even more hopeless when it comes to reporting. a social worker in australia told me once they dont even try to prosecute those cases because they are simply too hard to win and the parents are too smart to get found guilty and they dont have enough resources even for the physical and sexual abuse cases.
my two cents is try to keep ur connection with the girl. u can be her enlightened witness if u know what that means. it is an alice miller term and i think it is probably better than a therapist. and definitely less expensive and also in this case the girl won't be seeing a therapist it seems so u are pretty much her only "witness" - u understand abuse so i have a lot of faith in u and ur instincts.
but still it is a huge responsibility to know this info. i have been there in a lot of cases so i can relate. hug again