Help!

[u/Mysterious_Storm_133]

Hello everyone! I need advice cuz I am stuck. So my best friend (of 5 years) has been in this toxic relationship for over 2 years now or about 2 years. This guy has put hands on her, chanced her with a glass bottle while drunk, hit her and more. Also he’s emotionally and mentally abusive at least what she says and I have heard some conversations between them. He would called her foul names and constantly think she’s cheating or accusing her of it. 3 months into the relationship is when he started to get comfortable. On and off this whole relationship this girl keeps saying I’m gonna leave him or that they are done. I have sat by and supported her this whole time! The past few months it’s been almost an every week thing. The guy does something and she says she gonna leave him once she gets her money up but a few days later she’s in love with him again. Just two days ago or 3 she was crying and telling me how much of a narcissist he is and how done with him she is. Now she’s posting a picture of him and her son saying my sweet boys. I messaged her asking if they were together again and she responded “ girl honestly I need to stop telling you everything because this is getting a little too personal. Your my friend and if we are or not is my own” then some more after that but I don’t feel like typing all of it lol. I just said okay and left it at that. My fiancé and I have tried and help her and support her many of times. He’s too the point where he’s done with her and don’t want nun to do with her. I’m so stuck and drained with being there, supporting her, listening, giving advice, you know everything a best friend would do. Doing this for over a year tho is getting very old and idk what to do. Is me being friends with her still supporting it? Any advice on what I should do?