Why would she blame us?

When I was 7 my dad died. 2 years later my mother got married to this pevert. He molested my older sister and gave me and my siblings weed and alcohol. We were so young and my mom didn't care about us. My sister told her about the abuse and she ignored it and let it happen. Now it's all over she divorced him but not because he did anything to us but because one of her friends seen him give us weed and told her. My mothers all about her self image so she divorced him. Yesterday I was thinking bout all this and I texted her all mad and said your a horrible person and one day u will pay for what u let happen to us. She called my older sister and blamed her told her he did that to u cause u was all over him never left his side. After years of repressing her feelings my sister freaked out on her and said this is all ur fault u brang him to our life and threw us to him. I was ten and didn't know anything and u let him molest me and said nothing to him which made him feel it was ok to do it. I was so proud of my sister she never opened up about it til lastnight. I can't believe my mother never cared y have us if u don't want us and she really doesn't I never got put into any school activity because she would pay for it. she was too busy going out with friends. just don't understand how a women can have kids and not care about them that's so evil. I'm a new mom and there's nothing in this world I wouldn't do to protect and love my baby. How do u feel about my situation