@Spanielmad thanks for the update.
I think you (and she) need to let go of the idea that she would be looking at an A in ? history or whatever when she is looking at a D in maths – unless her maths is really weak (but then why take A level?). It’s not an easy A level, but none of them are.
I also think to say the B prediction is current rather than optimistic is a bit optimistic of you… I agree with @mrsm43s, sixth-form teachers know what they are doing, they are saying what this student is likely to get in the exams in the summer and in some (many) cases they over-predict, giving the best-possible-case grade.
I hear you though on the one poorer grade dragging her down. Don’t think like that tho and nor should she as it’s not helpful. What unis have you looked at?
Some suggestions:
Leicester – book offer for geog BA is ABB – my DD went there on clearing with BCC for a course with a book offer of ABB IIRC. It is a great uni and a good city to study in. It flies under the radar bc it is not RG but it offers excellent teaching (for DD’s subject anyway) and a diverse student body. It’s a good location too. I see @trivialMorning and@Cakeandusername agree it's worth a look.
Nottingham Trent – BSc in geog is 104 – 112 tariff points (104 = ACD). Another great uni that is perhaps overlooked bc of the big campus down the road, but I know lots of ppl who have studied here and had great experiences. Another excellent city as well.
Newcastle – again ABB is its offer and tho it is RG it is not as popular as some on that list. Marvellous city and lovely uni. No experience of whether it goes below its offer but it wouldn’t surprise me (whereas it would if we were talking about LSE or Durham).
UEA in Norwich, another good uni that is underrated by some. Again book offer is ABB but I bet there is some flex there. Highly rated by those who go there but not RG.
I also agree with others' suggestion of Lancaster - another that is sometimes overlooked in the race for Durham/Bristol/Leeds/London.
For some of these I mention she may get an offer with her PGs. Some may appear in clearing with a lower offer than they say initially. Tho there is no guarantee of that from year to year.
If she is looking at A/Astar-B-D (her PGs) then I don’t agree that there is nothing; plenty of newer but excellent unis like NTU, Sheffield Hallam, UWE (112 UCAS points – A-starCD – for geog BA), Leeds Beckett and more are looking for those kinds of grades.
Also yy – have you looked at a tutor for maths? If she could get that grade to a C it would be a big help.