University does allow to attempt failed subject in next semester to clear it. This is rule in all universities. It is unfortunate that she missed to give exam. Irrespective of subjects failed or results awaiting, students are allowed to attempt next semester exam.
But if you have backlog in any semester then you been not allowed to go in next year until you clear or pass it or in 3rd semester if it falls in new year. Make sure to keep eye on college notice board for all notification of university. Notification contains all details of eligible students for exam. Accordingly you can pay the exam fees and attempt exam. Please get in touch with college office for more details.