At 98 I am afraid that some poor people lose the bits of brain that control their emotions, so they can get pretty ratty. What a burden for you.
I am not surprised you feel drained - get some help in, so you can get a break. She will of course object to that but, as my DD says to me, "You can't pour from an empty jug." So you need to look after yourself.
If your Mum has sufficient funds that she has to pay for any care that goes in, the LA can put a legal charge on her property and recoup the money at a later stage.
You are entitled to a Carers' Assessment from social services - demand one!!
What an exhausting life for you.