I was abused by my step father who also physically abused my mother and siblings, I didn't live with her but had to visit which is when he sexually assaulted and raped me, I was 9 years old.
I actually have a reasonable relationship with my mother, mainly because we do not discuss it and I have moved past the pain and anger and have after a lot of years come to terms with what happened.
My mother did not protect me, I have never spoken to her about it, but someone else has within my family and she thinks it is a pack of lies, I think it is a form of fear that I have never confronted this, our relationship is fragile and held together by a dying old lady (my gran) and her great relationship with my daughter.
For me it has been my decision to move on and my refusal to allow the disgusting man the right to have power over me that has allowed me to come to this point, but for 18 years I was bordering on alcoholism, self harmed, suffered and still suffer from long term disconnections and PTSD from the abuse.
I will never, ever understand or forgive her reactions, and it may not be healthy but the older she get the more I feel sympathy towards her, or maybe it is me getting older.
Either way I am rambling... You need to do whatever keeps you healthy OP