i’m so sorry this is happening, i had a similar situation a few years ago. had a long time friend, but she would only ever drag me down. when i realized how poorly she was treating me, i did my best to distance myself from her. now three ish years later im so much happier because she held me back and now im free! since then i have made amazing friends, and we mutually support each other. it’s not going to be easy separating yourself from her, but trust me it is the best possible outcome. your…
It seems like you know what you have to do though. You have to fight for your peace and this person is not bringing you peace. Its not your problem that she doesn't like herself and her life so don't ever feel guilty for that. At the very least if you won't end this, keep her at a distance until she can heal