I was going to suggest wipes too, it can get really warm in hospital and it can be a beggar finding people who have time to get to get a towel and such so wipes are good for a quicker wash if needed between showers.
Clean towels might be useful too which can be replaced for the above reason.
If she will be washing herself, a nice shower gel and shampoo is good as the stuff they have there isn't great, something a bit of a treat is nice for a bit of a boost.
I find cordial great as it makes a nice change to just water, especially if the water has been sat there in a jug for a while.
A typed list of medication, dosage, frequency and any special instructions would be useful, especially if a few meds. It can save staff time in writing it down from memory and having it available for anyone who needs to know like nurses, consultants and pharmacy.
Some nice treats, maybe something some favourite sweets or a basket of fruit or something like that.
Caution with any valuables, especially if they will be left unattended, there have been a number of thefts locally from hospitals and last time I was in they told me never to leave anything valuable unattended and take my handbag with me whenever I left the room.
A pad of paper and pen, always useful for writing things down such as medical information or a list of things she might find useful (at the time) for someone to bring in for her etc...
Check the rates (if any) for any hospital TV and/or wifi or internet if she uses that. The charges can be quite steep and some places are sneaky in that the time runs from first view so, say if you get a 12 hour card, if she started watching something at say 7pm, it would run out at 7am so potentially wasted overnight. Maybe TV guide magazine so she could see what is on and plan any TV watching around charges.