My sisters stonewalling has ruined me

I feel ruined by my sisters abuse. I’m so unhappy every day and my mental health has just plummeted. I burst into tears yesterday and I just can’t stop crying I didn’t realise how low I was. My sisters silent treatment stonewalling of me and my parents enabling of her behaviour just chops away at me every day. I go round in circles of getting so fed up and isolated by it and eventually having to talk to my parents about it. Just talking to them fills with me with so much anxiety and every single time even when I’ve cried they just shut me down. The conversation reverts to them and how unhappy this situation makes them feel. I cant take this anymore my sister is such a horrible human being but just her conversations with my boyfriend even though I know he finds her strange and my parents kill me every day she makes me feel like an awful awful human being.