My mum knew my abuser was a pedophile and still let him babysit.

I accidentally overheard a phone call in which my mum said her step-dad sexually abused her when she was a teenager. I know I shouldn't have heard it, and logically I know that I should be upset she went through that, that this is his wrongdoing and not hers - but I just keep getting stuck on the fact that she KNEW he was a pedophile and still allowed him to babysit me (f27) and my brother (m29).

I was under the age of 10 the first time he put his penis in my hands. I was 19 the last time he kissed me. She knew what he was. I just don't understand why she'd allow him near us. She sat through countless mental health appointments trying to figure out why I started self harming, stopped going to school, stopped going out, attempted suicide and not once can I recall her even attempting to talk to me about it. Why would you allow the man that abused you near your children?

I don't know what to say. I don't know what to do. I don't even want to look at her. How am I ever supposed to accept this?