All little girls love to be fancy. Give her nail polish and hair bows, and lip gloss - assuming mom is okay with "make-up." Similarly, bubble bath and lotions if they aren't physically a problem. I would think that being in a wheel chair, enouraging physical touch and sensations would be very important to her.
Also, do they decorate her wheel chair? I went to school with a little boy who had bike streamers and a flag on his wheelchair. But I also know some people say to focus on the child not the device, so it really would depend on the parents' perspective.
I also love when people give my daughter music cds, especially unique ones. Maybe audio books?