Fairycakes, its understood that you may not have been familiar with the system, but your DD should have made sure she was.
There is loads of information out there, including on Student Room, albeit with a pinch of salt.
Small sample again, but I think people can sometimes be surprised at how competitive top Universities are. The English, as you no doubt know, are odd. Its not done to say your child is bright or special - unless you are on MN where obvioously every child is brilliant. Nor is it done to be seen to make too much effort. In central London it took me ages to realise that some of the kids being touted by their parents as absolutely brilliant, musical, artistic and sporty were rather pedestrian, though often very coached and tutored. I think it has taken even longer for some of the non-dom parents used to different systems where marks, class-rankings etc all count, to realise that their children are not necessarily brighter or better, and that tutoring only compensates so much for lack of natural talent. The girls with the best GCSE results at DDs school were NOT the ones whose parents thought they should be top of the form in Y7, indeed were often the ones whose parents made no special claims at all. Your DD sounds as if she is extremely bright, but it will be difficult to know how bright others were competing for the same places.
Your daughter seems to have got three good offers and two rejections. DS got 2 offers and three rejections. Both will be fine, they can only attend one University. The system here means that people don't get as worked up about rankings as they might elsewhere. Yes there is a bit of Oxbridge or bust, but for many subjects there are other departments who have a competitive offer. Lots of things in England are a bit fuzzy and not too clear, so relatively easy to find things to complain about. However HE, NHS and lots of other things work reasonably well and indeed often better than elsewhere. Relax.