How can I find the strength and courage to face my Mother?

This is really hard for me to put together. It’s my first time feeling that I have to do something about this and feel that I Don’t have to be SCARED anymore. It’s also my first time that I don’t want to just Run Away. I wanted to ask how I can tell my mother, who I don’t have a good relationship with, that for years my father sexually abused me. I think she already knows what he was doing but never attempted to do anything about it. I remember when I was about 9, she asked me if he was doing something to me, I was scared to tell her the truth because he had made me feel that if I ever told anyone especially my mother that I would be in such big trouble , soI lied and said NO. I don’t understand how after she felt that he was doing something to me, why would she still leave me alone with him. I also don’t understand how as a mother you would let your husband sleep in your daughter’s room after coming home drunk or at all. Why didn’t she protect me? Was she in it? He sometimes would come in my room late at night and bother me. I’m so confused on how this could ever happen to a child with having a mother around. I regret the day I had a chance to to tell her the truth because Now, I feel that she won’t believe me. I’m also afraid of the outcome of my speaking out. I feel that since it happened years ago, and he’s not in my life at all, why should I hurt anyone else by bringing the past back in. Another reason why I’m scared to tell her is because my father got arrested for sleeping with a minor, which was relative who was visiting for about a month, she was young and scared but strong enough to speak out. He got arrested and deported and my mother “Blames Her”. What’s wrong with my mother? Why, How could She still Love and defend this monster.