If you're staying there, you can drive a car to your campsite and keep it there. That's one of the Ft. Wilderness benefits- you can have your car right next to you. What you can't do is drive a car into the resort (past the parking lot in the Outpost upfront) if you're not staying at Fort Wilderness, in order to have a meal at the Settlement, for example. There is no car parking at the Settlement, next to Hoop Dee Doo or Mickey's Backyard BBQ, the boat launch to MK, nor any car parking at the resort pool. Perhaps that is what confused you.
When we camped, we didn't have a car, so a CM in a Ft. Wilderness golf cart took us and our gear to our tent site, and from our tent site the morning we departed (even though it was pre-dawn- it's a service they provide.) No worries- your aunt won't have to walk her gear anywhere.