My daughter had the same thing happen to her. She worked summer ‘24 on night sort and was told to reapply for peak when she was on winter break from college and they would throw her back where she was. Went online to apply and was not applicable. One night when I was in I stoped and talked with the night hub manager about it and he even confirmed with her direct supervisor that they wanted her back. They had to reach out to HR and have the problem fixed. Apparently it was an accident and she is welcome back anytime though she ended up missing the rehire deadline for peak. So she went to FedEx which happens to be next door and got a job instantly there. It seems to work better for college kids as well. Though she may come back to UPS in the summer and work both so she can get a heads up on her college loans.
So, have her reach out to her manager at the time and see if they can rectify the issue.