I second policy on posh pyjamas
(and I'm very very sad for both of you)
Lots of these that follow aren't really Christmas presents but might help over the coming year..
The things that gave my mother great pleasure were:
painted toe nails (she could look at them and still lie down!) so maybe a gift set of her type of colours?
audio books of things she'd not read yet, if reading is too tiring.
(Even better, someone reading aloud from books she'd already read ((pride and prejudice, georgette heyer etc) but you can't give that as a christmas present..)
ANYTHING to do with grandchildren! audio or vidoe recordings of daily life - stupid stuff, silly songs, counting from one to ten for little ones, explaining things like where does rain come from for big ones) and any drawing or writing that they want to do (tho don't stress about it and start forcing them to do stuff or you'll go mental)
A lovely painting? I knew my mother's taste quite well, if you know your dsm's taste, this is a good one. Neednt' be actual painting, poster of painting good. But you must say to her that she can just rest it against the wall (in case she looooathes it!)
Food is fine from the rest of them - my mother took tiny tastes of stuff even when very very ill, and enjoyed the luxury.
Cashmere knitted blanket (try Brora) if money no object.
cashmere bedsocks (Brora again) if money tight but not desperately so(£30??)
A hairdresser at home - do you have a hairdresser friend? I think, also, that Macmillan can recommend local ones, but not sure about that. check it out, she might enjoy some mindless 'been anywhere nice?' normality. You might say 'it's all booked and paid for already, can't get the money back now, it would be a shame to let it go to waste, what date d'you reckon?'
Do you have a digital camera? A cheap scrapbook of photos of the next month or so - not just 'cheese!" ones but just normal life, printed and stuck in, would be really nice, especially if you were able to get over to other family members and grab some shots of them. Although whether you feel this is apporpriate I think it depends on the stage of her illness - but maybe do it anyway and keep? And give it to both your dad and your dsm so it doesn't seem too pointed.
You - you sound lovely.