She will only be able to make reservations for her day of arrival and the day after her night on site.
If you think that's bad, consider this: We're staying on site our entire trip, but because we're changing from one Disney resort to another, we can't make reservations for the 2nd half of our trip until 180 days from the 2nd reservation. Even though we'll be on site the entire time, they can't link the 2 reservations together...