I hadn't heard about the nerve damage before, but on my last visit to the ENT he did say the surgery and rad probably created some scar tissue that would make some areas of my mouth ultra sensitive to some things like spicy, heat and cold. It doesn't sound like my problem is near as severe as your mother's though.
What I can relate to is the rainbow of pills that can happen, almost without one even knowing about it. Happened to both my past wives, at the end of the day I had to have a hazmat team clean out the medicine cabinet almost.
How many doctors are prescribing meds? Do they even bother to look at one another's prescriptions? Are you going to just ONE pharmacy to have them filled, and are you on a first name basis with the pharmacist. That sounds crazy, but we did that with my first wife and he helped quite a bit and spotted some things that might have been contra-indicated or interactive that might not have been too good to take. If you don't have a PDR, it would be a good idea to pick one up. Kind of into the technical jargon, but one needs to really understand what medicine one is taking.
I'm sure some others have some more useful suggestons, but there's my perspective, been there a couple of times, and that didn't even count my go around. I stopped the docs at 3 pills a session when I was in the hospital, told them you only get to feed me 3, which ones do you want to feed me, pick the top 3 and scrap the rest. Started getting nauseous from the pills themselves, said, nah, this ain't gonna work.
Hope your mom does better soon. Don't forget to take care of yourself, you can't take care of your mom if you don't keep yourself healty.