Yes, this is serious. You can tell your family I think so.
By all means — get her to her doctor. It’s possible that her behavior is the result of a vitamin deficiency. Really, I’ve seen it before. But it’s also possible that she is in the early stages of Alzheimers or some other dementia. Only a physician will be able to tease out what is wrong — and give you suggestions for treatment. See if the doctor can give you some advice about how to get her in for an exam. He might, for example, be willing to have his staff call her with a reminder that she is due for a physical.
Your mother is fortunate to have such a caring daughter in spite of her negative, even abusive, behavior. Just because she can’t acknowledge it doesn’t mean it isn’t so. You are being very good to her.
I wish you well.