I agree that she needs to talk to her doctor to see how realistic a trip to WDW is right now. If she needs her leg elevated at all times, she won’t be able to do anything except shows. Many attractions require a transfer and those that have a wheelchair accessible ride car usually are going to be too short to accommodate a wheelchair with elevated leg rest.
If it’s OK with the doctor, your only option would be a manual (push) wheelchair with elevated footrest. I’d suggest Orlando Medical Rentals - they have the most variety of more specialized medical equipment.
You should not have an issue with delivery to Swan/Dolphin.
Power wheelchair won’t be an option.
A small number of people’s personal power wheelchairs have elevating footrests, but rental ones don’t have elevating footrests that I have ever seen.
Most of the companies that rent power wheelchairs won’t rent one to someone who is not experienced driving one. They do have a learning curve to be able to drive safely.
ECVs have no footrests, just a floor. If she only needs it elevated a little, I have seen people using the 4 wheeled models with something on the floor to elevate the foot a small amount. The 4 wheeled ones have more flat floor space because they are kind of rectangular footprint. The 3 wheeled models are more manouverable and csn turn tighter, but the front is more triangle shaped, so less room for feet.