Welcome to Beyond Blue and well done for reaching out.
It's hard to try and help someone who doesn't want to be helped. And harder still when a relationship becomes 'unbalanced' as a result.
I'd like to suggest that even if she does not want to see a doctor or a counselor, that you could perhaps still see a doctor or counselor on your own, yeah? It might help you to make whatever decisions you need to make, in order to perhaps prevent your own mental health from sliding down even further than it already is.
It's great that you are working though, and that you are being as supportive as you are. It's a big, brave, and very challenging role to be the main provider. And I will also say, from past experience, that it is also hard having to rely on someone else so heavily. We all like to be independent, and to support the ones we love too, but when those roles are constantly swaying in the one direction, then yeah, the relationship can begin to topple.
Obviously I/we cannot tell you what you should or shouldn't do, but what I can and will tell you is this; you are not responsible for what SHE chooses to do to herself if you do decide to leave. And who knows, maybe a separation - even if it is just temporary - could be just the thing she needs to give her that 'jolt' into taking some action to make the changes needed?
Please note also that I am certainly no professional relationship expert - I've have my own fair share of relationship mishaps - but I do hope that helps at least a little? The good thing about BB is that it is pretty much 'open' 24/7, so you can come here for advice (or even a little venting) as much as you like. After all, we're here to help, if we can.
Anyway, if you want to respond then please feel free to do so. And if not, that's okay too. Take care. I'll be thinking of you. xo