My son has had several hospital stays as has a friend of mine's daughter. Here are a few ideas:
Things that make her feel pretty: An easy on and off night gown (hospital gowns are awful). Lip gloss/chap stick, lotion, pretty hair clips.
For my son we pretended we were on a camp out. We had a flashlight, made a tent with blankets, and I brought him some "camping supplies". We told scary stories (not really scary, he was only four).
Basically, they can't do much, but also get bored very quick. Another idea is a good movie she hasn't seen.
That's very sweet of you to go visit. Also, see if the parents need anything. It seemed like I never ate when my son was in the hospital. If he couldn't eat, I wouldn't eat around him, but also didn't want to leave his side.