In which case it may be somewhat appropriate that she too is given priority, but for courses on her MAJOR track (where other Biology minors would then take second row). It goes both ways: there’ll be semesters where she’ll snap up the most sought-after Biology labs, while Art majors will have to show flexibility.
It’s not done in bad faith. There will be people with multiple majors or double-minors. It’s someone implicit in the word “priority” that one cannot reasonably expect that everyone’s secondary/tertiary choices will fit everyone’s preferred timeline.
Based on her school’s site on Studio Art minors:
“Any student choosing studio art as a minor must consult the chair of the Department of Art for program approval. It is recommended that students begin work for the minor not later than the beginning of the second year. Students electing to minor in studio art are required to take any six studio art courses and any two courses in art history.”
While I understand her disappointment, maybe she’ll be able to “knock off” some of the art history, or possibly general education requirements - and then have a more flexible timetable when the Department needs to give her priority placement next year in line with her minor.