gummy614 said: "Most theaters have just a couple accessible seats that are almost always all the way on the side or in the very back of the rear mezzanine / balcony."
I'm not sure this is actually true, especially that they would always be in the back of rear/mezz/balcony, but why not go the other way: What show(s) might you want to see? On Telecharge, every show has a Tab for Access Info on where seating is located; on Ticktmaster, you can select accessible seating right from the seating chart, etc.
It is also a different issue if you want a transfer seat or whether she has to remain in her wheelchair throughout the show. Many theaters hold good orchestra aisle transfer seats in the center of the house. But some houses do leave spots more further back and off to the side.
I know, Studio 54 has a wheelchair seat on the front row aisle of the center orchestra, and many of them have them in the back of center orchestra, as well. But nearly all of them will have a way for you to see every show, so it's more about what you want to see...