Are you still renting? If so, see if it's possible to rent a true twin and set it up with the bindings centered and the angles the same. This way she can ride goofy or regular and it wont matter.
She can focus on whichever way seems more natural, but can continue doing a little of both. Once she has several more days under her belt she will be pretty good at riding regular as well as switch; which would be pretty cool as she progresses.