She'll probably have tons of time for the extended essay; I had a rough draft finished by the start of senior year. But perhaps different schools schedule it differently; we were expected to work on it independently during the summer. However, in two of my IB classes (math and psych) we had to write fairly lengthy papers.
Doing IB definitely prepared me for college, but a huge difference is that in high school I was taking 7-8 classes at a time (most of which had daily homework), versus 4 classes in college (which met 2-3 times a week).
Given good accommodations, though, it could be great, especially if you're not worried about the IB exams themselves.
