Two thoughts:
1. Ivy schools don't permit grad students to play during an otherwise-eligible fifth year, so she already knows now she can't return to Princeton for a fifth year. That conference rule stands in contrast to every other D1 conference, which permits that arrangement, and is thus why she has announced much earlier than most student-athletes who have a fifth year of availability, but who will have completed their BA/BA by the end of their fourth.
2. I can only speak for a Stanford-type school, but most of our grad programs have fall or early winter admissions deadlines, and she may want to do her grad-transfer recruiting now to know which WBB programs would take her before she bothers applying to grad programs at various schools, since the application process can be a lot of work.