ok speaking from expierence... I been with a girl with massive depression... Like really bad ( i hope yours isn,t that big into depression) Why? They see things negative as soon as you split up from a girl in severe depression they even forget about you and their emotions for you because there in that deep depression. There just so damm self involved and their problemns and very selfish. It even hurts to wright this (bad memories.... But in my case though even though the girl said that she loved me she always treated me like shit and could only talk about things negatively. I helped so much i tryed to get help for her and was the sweetest guy in the world (even bought roses which she even throwed away..) Bought her dvds and tryed to cheer her up by always talking and giving positive energy. And the only time i did get sex (once) she went to take the pill i asked her why and the answer was if she wants the sleep with other guys and they dont want to use condoms ( OMG!!!!!

that hurted) Anyways back to wheres it about.. I split it for a just a short while (2 months) cause i couldn,t take the way she was treating me. And when i contacted the girl again because i had to urge to help her. She said her emotions back then where just takin over (wtf?) blabla basically showed zero respect and had no emotions for me anymore. Basically i was a stranger to her (i helped the girl for 6 months and now i was a stranger...) and was so selfish about getting help for her depression i know it was a lost case anyway... After the girl said i was the main for all her problems and i was just a burden( yes these kind of people say these things to you even if you helped them and cared a lot about them) i just let it go... I never heard from this girl again...
BUT HERE IS THE CLUE:
1.
Stick with her and get her help and get her tru it (Only do this if your truly love eachother(and she treats you right which was never the case for me it was a bitch to begin with). Anyway cecause its incredibley hard and it takes atleast a year to get out of a big depression like that.
2.
Split up and never contact her again. There is 99 procent risc (if she is into severe-suicide depression that she wont feel anything for you when you contact her again( no matter how much you did and how true the love was). This is because these people just cant anymore they just forget you.. DONT TAKE IT PERSONAL. (i did got hurt very bad)