I'll jump in, seeing as this is actually my day job.
In terms of the University, she will need to submit an extenuating circumstances form to the University explaining what happened. As a general rule extenuating circumstances (sometimes called serious adverse circumstances or mitigating circumstances) need to be UNFORSEEN and OUTSIDE OF YOUR CONTROL.
Many universities are reluctant to consider transport delays as extenuating circumstances, but they will do so in extreme cases. If your daughter is able to explain what happened, why it wasn't her fault, and explain why she couldn't take any other alternative form of transport (including paying, from her own pocket, for a taxi from Settle) then they may look on it sympathetically. Part of this will depend on whether she ever attended the exam, or whether she decided not to attend because she was so late.
If the ECs are accepted the student will normally be allowed a resit at the next examination period, without a mark penalty, if the student failed the exam. If the exam was passed a resit opportunity is often not allowed, but it depends on the university. When the resit is depends on the University. At my current employer it is in the August, but at my previous employer it is the May of the following year, meaning a delay to graduation of twelve months. The student will not be in attendance for that period- so she will not be allowed to attend lectures and tutorials. In extreme cases the University's examinations board can allow a student to get an "aegrotat" degree, i.e. one where they award a degree based on the passed modules, but this is usually restricted to where a student falls ill and is unlikely to ever fully recover.
If the ECs are rejected then whatever mark she obtained will stand. Some universities allow students to resit final exams, and some do not; my current employer does but my previous employer did not.
I would strongly recommend that your daughter seeks urgent advice from the advice centre within her university's student union. Each University has slightly different rules on when you can submit ECs- at my current employer they must be submitted within seven days of the exam.