I was molested by my sister. I feel like I am losing my mind.

I posted before in a different group, but got victim blamed, so I hope I don't get blamed again in this group. My older sister started molesting me when I was 3 according to her. I, however, cannot even remember when it started. I just remember it always happening. It stopped when she was 15 because she felt that she has reached the age of accountability and did not want God to punish her for molesting me. I thought it was normal because it has happened since before I could remember, and I had a friend who's older sister did the same to her. I asked my sister when she was 15 how it started. She said we caught our dad watching lesbian porn and my 3 year old self convinced my sister to do what was happening in the porno. Well first off, I was 3. I could barely talk. I didn't even know what porn was, yet she blamed me for it. I know for a fact she had never been raped or molested. Now I know that her friends watched porn, showed her, and she decided to use me as a guinea pig. She even molested our brother who is close in age to me except she only did it twice to him. Throughout all those years, my mom caught her twice and didn't do anything. She just said it was kids being curious, so I didn't report it or tell anyone else until I was an adult. The problem I am having now is this. I have always been super close to my grandma. More than my siblings. I even stayed with her for awhile. She started having trouble paying her bills, so we moved in together, so I could help her. My sister is a user. She rarely comes around unless she needs something, so I would rarely see her. Well she got evicted from her place, and now she is over at our place everyday. I have told my grandma everything that happened before with her, and she doesn't believe me, and she still lets my sister come over. I am so angry, hurt, and betrayed. I feel so suicidal. Please don't post any hotlines. I won't call them. I would feel like shit just moving into my own place and letting my grandma struggle to make it (no one else in my family will help her because they are all selfish) but I need to get away from my sister. I am in therapy, but I cannot bring myself to have the courage to tell him. I have always been victim blamed. What's the point if I'll just be victim blamed again? My sister still makes inappropriate comments about me too. She'll bring up my vagina or boobs, or make inappropriate comments like we should take a bath together like when we were kids. She molested me in the bath as kids. I hate her.

Edit: I have told my grandma how it hurts me having my sister over. She thinks I'm being overdramatic. This hurts so much because I always thought I could count on my grandma, and I thought she loved me. She was even molested as a kid, yet she says this stuff to me.