Need some advice

So I have ptsd and because of that I avoid going to one particular place where we (my husband and my kids and I) use to live that triggers bad memories which is my parent’s house. My parents didn’t do nothing but they for sure didn’t do nothing to help. (My husband didn’t help either only because he didn’t want to get involved) It was the other people that still live there with my parents. Well because of that I haven’t visited my parents for 4 years. Well when I mean visit, it means I haven’t visited my parents house. So when I want to see my parents, my babe picks them up and he takes them to my home. Well, anyways my sister just messaged me saying that she coming in two weeks and if I want to see her, she will be at my parents house which I don’t understand because she knows how I feel about going over there . (My sister lives 4 hours away from where I live) I love my sister. She is my best friend and I will do anything for her. For anything she have ask and will never say no to her but this time I just feel like I cant especially that the people that tormented me still lives there at my parents. I feel like I’m not ready. I know I should just forgive and forget but I just can’t. I usually do with other people but with them I just can’t. They where and still are awful to me. So I just want to ask what would you do? Because I don’t want my sister feelings to get hurt because I didn’t went to see her but I just know if I go there, my anxiety is going to get to me. The last time I went there I had an anxiety attack.