all the advice I am getting is that GCSEs are totally irrelevant! Apparently, they are the past and mean nothing, particularly as she did well in them by fluke and bluff!
It is a shame that that is all you have taken from those posts. Those posts are in relation to you trying to use your DD's GCSE grades to dictate her current predicted A Level grades.
All posters are pointing out is that they are not used when teachers are producing predicted grades, due to the fact that they are studied in a different way (most revision done in class or booster sessions after school, for example) and that in the past two years, with the introduction of the new 9-1 GCSEs, the grades have been generated differently to how they have been before (which is a whole other thread!).
I wasn't being goady previously, as you accused me of being. The year your DD sat her GCSEs, the grade boundaries were far far lower to where they had ever been before, which you can check, because the papers across the subjects were much harder for the students nationally, so even more reason not to base the fact she surpassed her predicted grades back then (because her predicted grades at that time would have been a guess at best. There were many many many threads on Mumsnet about it, at the time). This is not to diminish your DD's achievements. Those are her results and she should be proud of them. It is just difficult to understand the mess Michael Gove left and why it is so different to students taking their GCSEs even just a year earlier.
Of course GCSEs are relevant as qualifications themselves, especially as more and more universities are having to use them because most Year 12s don't sit public AS exams anymore. For the ones that do, such as your DD, those grades are wiped anyway, should they carry them on to the Linear A Level. No longer are A Levels split into 'some marks coming from Year 12 and the rest from Year 13'.
This might help to understand why your DD currently has the 3 Cs for her subjects (the AS levels are much easier than the actual A Levels) and help you and here see what you can change, in order to increase them.
I would also like to add, that she can also apply to courses that are asking for Bs etc. They do give offers currently to those with predicted grades lower than advertised. A stellar personal statement helps with this. Best to contact the courses she is interested in, to check. This can also ease some of her pressure.