I don't know if it affects your chances of being accepted again or not, but she'd have to go through the full process again (unless she took the WBI late enough that September would be within the 6 month window)
As long as you cancel before traditions, it shouldn't affect you. I had a friend check in then go home the next day due to family emergency. He was accepted the next season.
Thanks. Her WBI was in March so September is the 6 month cut-off, so she'd have to completely reapply, I think, depending on actual date and when they open Spring enrollment.