when Mil was in hospital, we got her a bed jacket - like a dressing gown but long cardigan length rather than full dressing gown length.
Meant she could sit in bed and still be cosy without the hassle of the longer length dressing gown to sit on and get in the way - particularly important if she is going to have her hip done.
We got the one for mil at M&S - they had quite a few at the time, have just had a quick look and they have a few - two main types shown below; more colours on their website. But gives you an idea of the sort of thing I mean. They might want to have a long dressing gown with them too for walking to the loo or going to the day room, but a bed jacket type thing (even if it's just a nice hoodie rather than a special bed one!) is definitely useful when spending lots of time in bed. mil used to like to wear hers once she got home - she would get up and make herself breakfast in bed and read a book, and would wear it then.
more like a very short dressing gown
like a little jacket but in snuggly shiny fleece
Other things useful included lip balm/little tin of vaseline, some little bottles of water/lemonade/squash or cordial/things she likes to drink to make a change from the jugs of water, decent bottle or reusable cup to drink from so that if it gets knocked over it won't spill, little clip on book light or torch so she can read or see stuff if it's dark, very cheap crocs or similar that can be used as slippers and to go in showers and loos etc without removing, so feet don't need to touch the floor if it's dirty, and then chucked afterwards if necessary, nice wipes - for hands (before/after eating), body (to freshen up if she is unable to get to a shower), face, etc. Maybe dry shampoo. ear plugs.
asda at one time did a range of underwear/night wear for women going into hospital that was specially designed to be easy to put on, be in bed with, have access to bits for wires and tubes and whatnots, not sure if they still do it or anybody else does.
small thin photobook or album with a few favourite photos in of loved ones
small laminated card with all useful contact numbers on so she doesn't have to remember them
A thin over the shoulder tote bag to carry stuff around with her if she doesn't have hands free (depending on what she is up to - be it using a wheel chair or crutches or walker). I like the mia tui sue shoppers which are only £4 and have 2 sections plus a zipped section in the middle for important bits but fold up small when not in use.
some long life food (ie nothing that needs a fridge or freezer or cooking) that can be eaten if she doesn't like the food on offer or is still hungry etc
eyepad if she likes to sleep in darkness
small vicks or olbas oil - great if there are unpleasant smells around that you want to mask but don't want to use up loads of perfume!