Who would think hearing aids could cause so much contention and distress, but THEY DO! Like you say, if you felt they were trying to help themselves as much as they could, you could be more understanding. My Dad goes as far as to say he doesnt want to wear them because he can't hear with them in. Funny how when he does have them in communication with everyone is easier. (I have put them in and you can hear a fly fart)
Just a thought, but maybe you could convince her to wear her hearing aids by simply being 'deaf' yourself to whatever it is she wants doing!
Just because she's old and infirm, doesn't give her the right to make other people's lives more difficult than they have to be, when they are doing things for her!
And if she doesn't like outsiders coming in, well, that's fine, as long as she doesn't expect you to do their work instead!
You can let her get away with some things - fair's fair after all! - but not get away with everything.