I have been going out of my way to accommodate my 84yr old mother food requests. I am understanding about taste buds issues of the elderly. My mom will ask for food to waste it. Then turns around within 20 min asking for something else. She remembers wasting the other food. She also refuses to eat leftovers. We can't afford it and I'm over it after 2yrs of it.
As was the case with my grandmother, it could potentially be dementia or Alzheimer's at work.
The food banks in my area have no income thresholds so that might be something to check into to help your budget.
I am just curious why you haven't told her to stuff her nasty threats and why you put up with someone that is all there, according to you, threatening your very freedom, because senior abuse is taken seriously and she is risking your life with her lies. Grow up and tell her that her free ride has just ended and her hateful a$$ is going to be placed for her own well-being and your life.
If there is nothing wrong with your mum - she's just old, but an adult nevertheless - then she should understand that you're not there to wait on her. She's lucky you are looking after her at all.
If your mum continues to make your life miserable, then you should part ways. There is no good reason to make your life worse for the sake of hers.