...I don't know where to start. hmmm
ok.
First lets start with your girlfriend.
Yes she is depressed, and suicidal but that doesn't make her any less of a human. Just like any relationship, set boundaries and rules.
No matter what, be tough with her. Take a moment to talk to her about her feelings and reasons for being depressed/suicidal.
You have the every right to know what is going on.
From what you are telling me. it seems like your gf is unsure about what do to herself.
Now about you
Dont think you are selfish for wanting to leave her.
If you tried your best and gave it your all but things still doesn't work out then i suggest you bail out or you may never move on with your life.
On what you can do
You should try forcing her to talk. Confront her. Tell her about the problems you are experiencing because of her.
Make her understand it is not all about her.
Right now she is taking advantage of you, did you know that?
You are acting more like her servant then her boyfriend.
Step up, and speak up and talk to her.
Tell her what you want out of this relationship and also tell her your expectations.
Ever heard of tough love? Practice it.
and lastly love her. Make sure she knows you love her.
I hope things turn out well and also keep us updated
Cheers,
Peter