The Ivy League, of which Brown is a member, only allow athletes to compete for four years from the first day they start classes(matriculate). There are no scholarships and there is no redshirting in the Ancient Eight. So a lot of Ivy athletes graduate with a year of eligilibity remaining (by NCAA standards, which normally allows five years to fit in four seasons of competing for the school), often because of injury or study abroad.
So Anna Willard is a graduate student at Michigan now, and is using her final year of eligibility at this time.
Michigan also got pretty Katie Gwyther from Quinnipiac, who was 12th in NCAA finals in cross country in her senior year at Quinnipiac. Not Ivy League, but she is another graduate student with a year of eligibility left, so the Wolverines scored twice.
Duke Graduate Student Emily McCabe, who graduated from Cornell, is Running for the Blue Devils in essentially the same situation as Anna Willard.
So Go Anna! Also a big hug for Aly Kohlmeier. Get well soon.