Little confused here. You state that she was there for athletics, but school had yet started. ROTC started after the 1st day of classes, which means if she passed her PFA at the 1st opportunity which is usually within the 1st few days, she would have been retro paid to the day she signed her commitment papers.
If I am correct she was there weeks early for an athletic program, not to attend school and get her degree, nor to train as a future officer. Why should they pay if her only reason to be at school before it started was her commitment to sports? They did not ask her to be part of any athletic team as a requirement to be in ROTC, did they?
Not trying to be rude, but that was her decision, not theirs, thus, impo, they should not be on the hook for it. Now if you said that they didn't give them their PFA until weeks after classes started than I am with you, but that is not the case you stated.
Think about how much they pay out in stipends per yr. Assume just 1000 cadets as 1st yrs, and you are talking about 4 million a yr in stipends alone, add books, and tuition, and you are way into the multi millions, now multiply that by 4 (4 yrs of school) and you can see why they say, nope no money until you contract and we don't care if your school makes you show up early, be it for freshmen orientation or a sports requirement.