The older I get (ugh) the more I feel that life is just one long exercise in prioritization...

I tend to put other people first, before myself. It is not a good thing at all. I'm pretty sure that's it's own mental health issue but that doesn't matter here. If she has this pattern that won't change, then I think you know whether you can stick it out with her or if your own health will suffer too much.

I think of my own mental health as kind of like currency for my relationships (odd, I know)....Some people, I gladly pay for. Some cost a little...some are totally out of my price range and I have to just walk on by.
In the future, I hope to be mentally wealthier... But I am not right now

I hope I make some sense....