If you have injury problems and/or were playing other fall sports, I can see how she decided not to compete in XC for her school.
The XC season for these schools is a "grind" with weekly meets from the second week of September till the week prior to Thanksgiving break. In with the few exceptions there is no indoor.
The New England Prep School Track season is very short as boarding school's graduate in early June and in some cases, the senior's do senior projects which in some cases have them away from "campus" for the balance of May.
So championships are held the second and third week of May.
My observation is that by and large the majority of these athletes are, in my opinion, under trained and over raced if once they graduate and head off to school.
Interesting that whomever is coaching/advising her has taken a long term view in her development.