I hope you do manage to get up for the start of S5 (and she can go into S5, which is the direct equivalent of Y12).
Just so that all her eggs aren't in one basket, make sure she visits other Unis who do similar courses: Glasgow, Strathclyde, Aberdeen, Dundee, Stirling, St Andrews (I've no idea whether they do the combination she wants).
Ds had his heart set on Edinburgh (mainly so he could play rugby there
) and even used up two of his five UCAS choices on similar courses there against my advice but he got rejected by both.
He didn't like the feel of St Andrews (fair enough: his reasons were exactly the reasons I'd loved it when I'd gone there 40 years ago
), applied to Strathclyde but not Glasgow (as when he visited they didn't do quite the course he wanted) and visited Aberdeen under duress from me.
In the event, he loved the feel of Aberdeen (it's also an "ancient" uni, sort of half way between St Andrews and Glasgow in feel), loved the course - and graduated from there last year, straight into a job in his (niche) field 
He got unconditional offers from Aberdeen and Strathclyde (Strathclyde just before Christmas, Aberdeen, iirc, in mid February) and was rejected by Edinburgh (x2) and Dundee, so there's no obvious logic - except perhaps his personal statement.
It meant he could relax a bit for the rest of S6, in which he was doing AHs in Physics and Maths and a crash Higher in Modern Studies (which was relevant for his degree).
That's another advantage for your dd going into S5: she can add to her Highers and/or do some Advanced Highers in S6 while she is applying to Uni and possibly even get unconditional offers. At the very least, she would already be part way to get the exams she needs.