1) Don't care what anyone else thinks.
2) Tell your DD that you will be getting an off site wheelchair for her so she and the rest of the family can have the best possible vacation.
3) Let her know that you know she doesn't need this all the time at home, but at WDW there is 8-10 miles of walking per day so it is best she conserve her walking for when she needs to.
4) Wheel her in line and then let her transfer when you get to the ride.
5) Don't care what anyone else thinks. Care that she is comfortable.