No she shouldn't be allowed.
They should just make transgendered bathrooms already.
Why? To treat them like aliens or what?
Well, as far as I know most of transgender-People make their way through the final operation (which takes some time to get there), so why shouldn't they be able to use the bathroom of their "real" gender?
It's not like they are raping anyone. And I don't think that People will peek into their pants to see if they are right there.