Extreme Sister issues

So my sister has hated for as long as I can remember 🙄 she blames me because she said the abuse she endured i didn't like its unfair and its my fault. She's gone out of her way for YEARS to attack my social life til I just said screw it n gave up on trying to have one. She's controlled who I was around by making people hate me and only approving or not totally sabotaging those who are like her which she still kinda started drama but I couldn't stand them anyways (they were like her) and all this. Hard to explain but anyway. She had her friend introduce me to someone who (listening to them in the bathroom) their plan was to screw him pin it on me n set in more social drama. Anyways. I called the girl out n put it on blast publicly and since me n him have been together 2 years. We have recently gotten engaged 💍. When I was talking to my grandma (I should note shes definitely not happy) about dress she heard n she said she wants to go dress shopping with me. I said ok not meaning sure but meaning thats weird. She said "I can't wait then I can pick out my dress and make it all about myself" n froze like she just realized our gramma was still there. Our grama looked at her like ugh.. anyways I want to move and elope and not have these problems but he won't. I know she's going to do her best to destroy the wedding and probably us. She is the worst person ever. I don't want any drama I'm more a humor person but idk what to do. Advise.