Is your Mum unwell already? You've said she already has trouble with appetite and drinking?
It didn't sound like she has had any Chemo as yet.
Don't push her to have fruit tingles or use the Paw Paw in her nostrils until she needs them. She may not need or like them.
I used vaseline in my nose, but only a few days I was bothered enough to need it. Just have these things available should she need them.
I guess stock up on the drinks and foods that she likes, you probably already have.
Definitely discuss with the Doctor/Oncologist, you mother's difficulty with intake.
My mother, when she had Chemo, was difficult too. We can only try, and do our best.
I do wish you both good luck and all the best.