Being dragged under by a close friend but still want to help

My friend and i are teens now and have known each other since kindergarten. She is the closest friend i have and i love her like a sister, but i have had severe depression the past several years and she is suicidal and relapses in self harm every few months. just recently we were walking across the street from each other and she casually told me she was six months pregnant and getting an abortion. she said she had been raped and but just shrugged because apparently it had happened before, too. i completely freaked out, but she said that it was easy to remove it and no big deal. her boyfriend also recently 'proposed' to her; he said it would've been fine if they kept the baby and that he would be happy to help her raise it!!!! Her parents are letting the boyfriend stay at the house with her, because things are not good at his house and apparently he will 'kill himself' if she doesn't stay with him. they were not raised normally and there is a history of mental illness in her family. the main influences in her life are not helpful-a PTSD drug-addict, an emotionally dependent boyfriend, a clueless father, and a mother that is too kind for everyone's good and helps other families before her own. i worry for her sweet younger brother who is the most normal of them all. my friend is very insecure and often unkind. she does not even pretend to listen when i speak, and has made me cry many times over the years in frustration at her inability to understand and change her nearsighted ways and her attempts at control and constant jealousy. she also comes across as an unassertive young girl who wants to please and be praised. i have not always been kind to her either- i often found myself to making assumptions going off about it. i try to control myself and keep waiting for her to change- but have i been wasting my time for years? i am finally starting to be motivated and make plans for my life. i am finally starting to be able to live outside my head. but i don't want to ignore her as i find my way out; we've been through so much together. i have other friends but none i am as close to. and i feel it would be wrong to stand by and watch a friend's life go to ruin, because i have suffered quite a bit and can only imagine what she's going through. she is on the spectrum and is often unable to get out of her head and grasp the enormity of a situation, and she often hurts herself in the desire to help others. she is emotionally immature yet sometimes surprisingly altruistic, and has comforted me many times when i was lost. i want to help her but i don't want to lose myself-what can i do? please help.

Thank you very much for your advice. You've helped me greatly in seeing that I need to take more care of myself, and now I know that one person cannot save another. Also thank you for reminding me that my own life is important too, something which I often forget.