because I really don't know what is considered 'best' for a 10 year old, here.
what is the balance between knowledge and safety, of trying to help maintain a relationship with her mother, but knowing that, when you send her, she is also experiencing trauma.
but coming home with drug paraphernalia should be a tipping point of some kind, shouldn't it? would reporting that ensure future visits are supervised by someone other than the grandmother?
I'm so glad she has you - to come get her when she's feeling scared or just to talk her through her scary moments.
I have no advice, my father's alcoholism was something my mother tried to hide from us - we would go on a lot of unexpected vacations, and we wouldn't call home when we did. I didn't know that was because of his alcoholism until years later.