How can I help her see her worth?

My oldest sister is transgender. Male to female. I was the only one in the family who supported her and cut off my family when they kicked her out of the family. When she first came out, I took her shopping for clothes, helped her with a her make up and did everything I could to make her feel better. She went through top and bottom surgery. She had gotten her first boyfriend. She loved him because he was the first guy who excepted her for who she was. My sister has some trauma. Back in High school before she came out as trans she originally came out as gay. So a bunch of boys called her a fag and she was gang raped behind the school.... She has a fear of being around large groups of people she doesn't know because she's scared it will happen again. Her boyfriend is honestly a complete ass and he always came off as an ass. So what happened was they were arguing and she went to her room and he grabbed her and tried to make her take her clothes off in front his friends so they can see her "Fake female body"( that was his words not mine). He tried to take her clothes off and she had a panic attack. He started recording her having a panic attack and posting it on snap chat. Thats how I saw it. All his friends were laughing while she was hyperventilating on the floor. I went to pick her up and her boyfriend's friend was trying to get grabby with me so I punched him in nose and I'm pretty sure I broke it. The next couple of days her and her boyfriend made up. I told her he's an abusive dick and sbe just said "He doesn't hit me" He doesn't have to. I feel like what he did is a type of abuse. I think she feels like he is the only one who will accept her for who she is. How can I help her see her worth?