Sounds very similar to my MIL, Jackie. She never really got over losing her husband - it was nearly 20 years ago, and she has just never moved on. She tells us that her life is dreadful, purely because she's on her own.
She also suffers with pain from arthritis, but most of her joint problems stem from the fact she just decided, about ten years ago, that she wasn't going to walk anywhere anymore. And she didn't ... but within a very short time, she couldn't walk anywhere anymore because everything seized up. She has one of these wheeled walker things (a Rollator?) but won't use it, so she never leaves the flat. Which has to be depressing in its own right.