There is actually *more* walking with the
DAS a lot of the time, as you need to go to the ride to get a return time, then go somewhere else while waiting for your return time. Even if you have a DAS, that will not eliminate walking or even most of the standing. The DAS does not work for most shows, parades, fireworks, restaurants, stores, meet & greets, Disney transportation, water parks, resorts, anything not in the parks itself, a lot of stuff.
And as others said, an ankle injury will not get the person a DAS. There is no reason to be embarrassed using a wheelchair. I would suggest a
scooter, though, as it is a LOT of work to push someone all day. She can try out scooters at a local store, though it does not take long to learn to use one.
If she is self conscious about what others think, she can always put an ankle brace on so there is a "visible" reason for using the scooter. But she will hardly be the only person using a scooter without a "visible" need. I certainly look "fine" and I use a wheelchair full time.
As others have said, most lines are entirely wheelchair accessible, so you go about your vacation as you usually do.
Really, this is all about enjoying your vacation, so who cares was some random strangers think?