OK, firstly you have to look after yourself. This is really important. It's not your fault this is happening.

Of course, it's not her fault either, but she's the one with the depression here. It's almost impossible to "fix" someone, all you can do is be there and point her in the right direction. Like encouraging her to go to therapy, maybe, even if she doesn't go.

Anger and depression often go hand in hand, it seems oft-quoted here on PC that "depression is anger turned inwards."

I think you're absolutely wonderful for doing what you're doing, but don't lose yourself in her fight. If she really wants to get better (and realising what your problem is is the first step) then she'll reach out somehow. Maybe she's not quite ready for that yet, so I guess all you can do is just sit there with her and be there when she's ready.

Also, I'd be wary at spending all your money on her meds, altho it is a nice thing to do... are there any alternate sources of funding? Government subsidies/ health insurance/ her family? If she is in chronic pain, would there be some kind of benefit from the government? (I'm in NZ, and here she could go on a sickness benefit probably).

At the end of the day, if it's too much to cope with, let her go. It's your life you may be messing up..