18 year old sister

My sister is turning 18 and we both grew up in a toxic household and I was able to get away back when I was 13. I personally have been forced not to have close relationship with them due to my ex husband and I had a baby and he would threat to divorce me. Finally I left him and got in regular contact with her. Sadly she’s SA a few times over the course and told her mom and her mom has torn her down called her attention seeking and a liar even though there was proof. I have finally moved into a nice place of my own and I could help her so much with college, and her mental health it was so bad she had talked about ending everything and got put in a ward for a week. Since she’s been out nothing has gotten better just worse with her and her mom. Her ex gf since she was 14 has offered her a way out but this girl has broken my sister heart from cheating and being toxic to leaving my sister to go date other girls. I don’t think it’s a good idea but they eventually end things badly aleast once a year. But I can give her a fresh start nobody knows her and she can be whoever she wants, and grow so much mental and physically. She 17 5’3 and 93 pounds because she wasn’t eating. I know that I can help her so much I have so many resources and opportunities for her here I just want give her a happy life she deserves and give her chance at new beginning I’m scared if she stays where she’s at and around those people I may not have a little sister one day. Please any advice or way I could convince her this life I could give her is far way better then going back to her ex who has a gf right now. I’m trying to hard to show her the amazing life she could have.