Coping with a friend that is chronically mentally ill... advice?

I accidentally posted this to Controversy Corner. Sorry. It was meant to be here.

My best friend of almost 15 years has been severely mentally ill with depression and anxiety for the past 3 years. About 7 years ago I moved away, got married, had kids, so our relationship is mostly on the phone minus the few times I’ve been home to visit. All around us, our friends have done the same as me, grown up, started careers, families, etc. However, my best friend still lives at home with her parents (we are in our 30s), doesn’t socialize with anyone, and has no real plans to “grow up” more than that. She complains about her parents constantly, says they’re toxic, annoying, and the cause of her mental health issues but she won’t move out.

For the past 2 years she’s been seeing a therapist who says she’s depressed and has anxiety. She takes medication and sees her therapist once a week but I haven’t seen any improvement. She disappears from the planet and then resurfaces and says she stayed in her bedroom for the past 72 hours and didn’t do anything. She works as a kindergarten teacher in a private school and they only pay her like $16 an hour, but she won’t change jobs to a public school to make more money (even tho she could because she has a degree) because she crumbles at any sort of routine change. The pandemic has made things even harder on her and she’s adopted some totalitarian views about masking, like thinking everyone should be forced to be vaccinated and her kindergartens should wear masks all day even though they’re only 5 years old.

It completely drains me when I talk to her because for the past 3 years it’s all been about her and her issues. She is constantly complaining about something or whining and never has time for me. I had a baby last year in the middle of the pandemic and it was like she did not even register it or care. I invited her to my house (a few states away) to stay but she won’t come. All we ever talk about is how depressed/anxious she is, how her parents caused her all this trauma, how she’s always going to be “fat and alone”, etc. etc.

I just don’t know what to do with our relationship anymore because I feel like I myself need a therapist to cope with her issues. Has anyone ever been in a similar boat?