My sis is miserable due to a breakup and it's effecting me and relationship?

I want her to be happy and do everything i can but she won't even follow up with doc appts. She is hugely depressed but this has been going on for a while. I do everything I can at the expense of the most part of my life. I am with someone I love but he's suffered greatly due to this. I have suffered for a long time and I don't even know how to cope anymore. She is the most negative person you'd ever meet and thinks that nobody can help her. Even advice goes out the window because she knows more. What should I do?My sis is miserable due to a breakup and it's effecting me and relationship?
this is very difficult. do you have. do you have other family members around or people she cares about and they care lots for her? if so you might need to do an intervention, like for an addicted person but in her case to address the depression and the negativty. does she have kids? b/c a way to a womans heart and to make her change is through her child, most of the time anyways. other than that you might just have to let her be. tell her that she is making you very unhappy and you and she cannot spend as much time together if she keeps acting this way. is she suicidal or just a mean person? b/c some people are negative while others are depressed and she sounds just mean. most depressed people would rather hide from the world then go out and about and make others miserable. just tell her you can chat on the phone or have a 1 lunch once per week w/o your spouse and maybe she will get the hint.