Hey, I know exactly how your mother feels, I've had PCS for 2 months and I'm suffering greatly with noise sensitivity. When our phone rings, which is just the same pitch and loudness as before, feels incredibly painful, as if someone stabbing a pickaxe through my head would be more pleasurable than the screech of the ringing phone.
Ear plugs are a fantastic suggestion, I'm about to get some for myself, as I struggle to deal with everyday sounds such as the tv or people talking. Also suggest she rests for a couple of hours, in darkness, for an hour or so most days. It really helps me feel more refreshed, alive and tolerate towards noises and lights. (Our christmas tree has flashing lights which result in horrible headaches)
I can sympathise with you and your mother with you father for not understanding. My family are still reluctant to accept that I have PCS and are finding it hard to adjust to my condition. But it's not that they don't understand, they're trying to cope in their on way, it's hard for them too, maybe your dad just needs some help expressing how it's affecting him. Because PCS does affect everyone, and it's scary to watch someone you love suffering, and feeling helpless... you know that...
I hope your mother recovers quickly, good luck