Bit of 'cutting your nose off to spite your face' here? There is a *huge* difference between Oxford and Cambridge and the 3rd best University for law. If she is as smart as you claim, she is missing out on a great education to make some childish point about snobbery. If she decides in future to work at the commercial bar, she might be worried by the fact that in the past few years not a single Magic Circle set of chambers took a non-Oxbridge pupil, so she has as good as written off that option.
And Oxford don't even offer an LLM so I doubt they care that they are unlikely to succeed in attracting her application. The Oxford BCL is the best Masters level Law course in the World, but hey, you have to sit in fancy buildings to do it so better off at University of East London, right?