Maybe you can bring in a therapist? If you think she's in depression maybe a psychiatrist or psych nurse too, but I'm not sure if you can find those who make house calls. Maybe some clergy could make house calls. It would reduce isolation and then she might have motivation to take steps further.
In that regard, see if your community has crisis services, or something of that nature. Here in Maine, there's an 800 number people can call 24/7 to talk to somebody with mental health training. They can also send out crisis workers day and night to meet with people and help them determine their next course of action.
I would also suggest talking to your uncle, to impress upon him the importance of the situation. If she's relying heavily on his medical opinion, perhaps he could talk to her and comfort her. I don't know how much of that has been done, but it might be an option. If he won't be helpful, then encourage your mother to get another opinion.
Lastly, I know a lot of people have had good luck with holistic approaches, but I wouldn't even know where to begin there.
I work in the "whole-istic" healing field and Tradeproposaldude, if your mother is afraid of western doctors or just doesn't like them, I would recommend she try acupuncture for her RA, poor equilibrium and most likely depression.
Here's a brief abstract from a research review article:
http://www.ncbi.nlm.nih.gov/pubmed/20204371*Note: for every pro-research article published there are numerous con-research articles published to refute them. So take all research articles with a grain of salt.
Also here's a brief youtube clip related with arthritis & acupuncture:
http://www.youtube.com/watch?v=t7t_9hfh8nM&feature=relmfuThe guy kinda looks like Wyc...but not really.
The thing is, you love and care about your mom, so it is time to take some assertive action. The current path your mom has taken since 2010 isn't working.
Have her try something, because sustaining the current status quo will most likely aggravate the unhealthy symptoms.
If you have any questions, don't hesitate to ask or send me a PM.
Good luck.