Hi Krystin! Welcome back to the Disney Parks Moms Panel!
You are asking a really great question and I am so happy to be able to help you! I love that you are planning ahead and thinking about making this trip easy for your travel companion! They are really lucky to be traveling with someone like you!
As you may already be aware of, there is A LOT of walking at the Walt Disney World Resort. Even those of us in decent shape find ourselves tired and sore at the end of the day, so for those who mobility issues it is very important to think about how best to accommodate that.
Wheelchairs are available to rent however, I do not know of complimentary wheelchairs in the Theme Parks for intermittent use. My recommendation would be to rent a wheelchair for the length of stay (if offered) for approximately $10 a day (prices are subject to change without notice.) This way your friend will have this available to them if/when they need it. Wheelchairs and Electric Conveyance Vehicles (ECVs) are available on a first come first serve basis. You also have the option to bring your own wheelchair into the Theme Parks, or you can also rent from one of the approved Disney Featured Providers. These approved providers will deliver your chair to your resort hotel upon arrival and will also pick it back up at the end of your vacation. All of the buses are accessible so you can take it to and from your resort hotel, to the Theme Parks, and back again.
I hope that I have helped to answer your question! Please visit us again real soon!
~Heather~