Eye shades, the kind with little cushiony things to actually hold the eyelids closed, and ear plugs. It's really really hard to sleep in a hospital with lights and sounds all the time. A water bottle with a built-in straw - the type that folds into the mouthpiece when you aren't using it. (Hospitals always give people a plastic pitcher and a styrofoam cup/straw, assuming it's going to be super-easy for you to sit up and drink/pour without spilling. A book of crossword puzzles, sudoku or one of those "variety puzzle" books from the magazine stand (something to do that doesn't require total silence or concentration) and a few mechanical pencils (always sharp, don't require a sharpener).
Slippers or socks with the non-skid bottoms on them. The hospital gives you some for walking to the bathroom but they're never all that cute!
Put her last name on everything with a sharpie or with a label she can tear off after the fact. If they move her from one room to another, which sometimes happens, or if the staff cleans up, they'll know which stuff is hers.
A "get well soon" note from your son, even if the letters are backwards or upside down. It's hard for a child in kindergarten who's going to be confused when his teacher isn't there, so this helps him get acclimated to the idea and gives her something to smile about.
Housecleaning is a good idea but she might not want all the parents in her home, so a gift card to a cleaning service might be good. You can also organize a meal chain though a free sign-up list called "Lotsa Helping Hands" - it can be done with a friend of hers or a fellow teacher she's close to, to incorporate various circles of friends and well-wishers. She determines the types of things she needs (including favorite foods and anything else like taking her children to activities or going grocery shopping), it gets added to the schedule along with instructions (such as "leave the meals in a cooler on the back porch after 4:30 PM" so she doesn't have to answer the door). Everyone can see what's needed and can sign up for what works for them. No more "Let me know what I can do for you" and then the teacher has to do all the organizing!