Refer to post Disabilities FAQs and specifically posts 2, 5 and 11. I don't know how to do a link for it.
For most rides you can take the
ECV through the ride queue like a wheelchair. There will be an area near the ride where you can park the ECV before getting onto the ride. In some cases the cast member will get the
scooter to the end of the ride if you don't make a loop.
In some cases you will use the same ride line as a wheelchair would do. For example, Toy Story Mania works this way in Hollywood Studios.
When doing boat rides it's best to have someone in front of her and in back of her to help her in and out.
I would advise practicing with the free scooters in the grocery stores and such before the trip. The store scooters are actually a little harder to use. If you have a local zoo try a scooter for a day there and that will be a good test run.
If you are using Disney transportation from the resorts to the parks with a scooter and especially buses this will probably take a little time getting use to getting the scooter on and off the bus. Sometimes, we would take over for the scooter driving on the bus and do this for them if they can manage to get on and off the bus themselves.
Renting off site will be way cheaper for a scooter and you will have it available at the resort, too. You do need to charge the scooter every night. Take the charger to the park just in case you need an emergency charge. Scooters should be rented based on the weight of the person. You shouldn't overload the scooter; this will cause problems with the scooter not lasting all day. For a heavier person get a stronger scooter. Some scooters come with two batteries and last longer.
If you plan on using a car with transporting a scooter to the park you will need a travel, portable scooter that comes apart. Learn how to take one apart and put back together again. You can go to a local mobility store to see how this works. There are u-tube videos, too that will show you how this works.