Not sure on your budget, but you would be the hippest aunt if you
gave her Nintendo DS. I would ask her mom first, cause it is a "video game", but based on her circumstances, it might be worthwhile investment to keep her from moving too much.
American Girl dolls may be a hit.
CDs or DVDs - High School Musical, Camp Rock and Jump In are the rage.
What about a small Kareoke (sp) machine....Gives her a different outlet to let off her energy. (Seven yr old girls love to demonstrate their angelic voices!) Anything with a mike. (I believe they even may make them with a CD player, not too expensive, and you can combine with one of the CDs listed above.
Hope these help! Glad she is recovering so well!
Best,
Barb