Whitesand -- I feel your pain, as had similar issue with DD2 earlier this term, whose AS grades in the subject she plans to study, plus one other, were not the best. Having spoken in desperation to a friend who's been an admissions tutor, I gleaned the following: unis are more interested in a candidate's GCSE profile and their predicted grades at A2 than they are in AS results, as most people realise something can go wrong at that transitional point and there is time (just) to improve.
DD2's school had been telling her that there was no point in putting down the RG uni she wanted as offer will be AAA and school maintained they would automatically exclude offering to anyone with less than an A at AS. School wanted her to put down only those unis which offered AAB or preferably ABB for her subject (History), which were basically ones she didn't want to go to, plus the point you make about just getting a degree, regardless.
In the end, DD2 put down a mix of top level options plus courses at less well-regarded unis where the course itself had something of interest (eg year abroad/particular aspect of History/special study centre etc). She also made sure her personal statement had lots about what she's read and where she's been to look at historical sites. Upshot is an offer from the uni she wanted, albeit at AAA, BUT (and this may be a big point for your DD, too) she is now hugely motivated to get the work done and get the grades.
So, my advice would be: tell your DD that her stellar GCSE grades will, actually, help her get a place, but she's got to think strategically. Of the 5 places, fine to have 1 or 2 as top level RG, but she needs to plan carefully for the others -- they either need to be combinations of her chosen subject with something else at RG uni (eg History and Philosophy degree offers are usually lower than straight History); or she needs to comb through the course descriptions at the various non-RG unis and find a course that really appeals or where the uni is outstanding, even if the rest of its options are more mixed. (Eg University of kent History course gets v good ratings in most of the league tables, and has special interest in war studies/propaganda, which could be appealing)
Where I do agree with her school is in getting her application in soon -- apart from anything else, as the offers start to happen (or not....) you get an idea of where things might be heading.