Hi again, OP -
Writing as a former admissions tutor:
the universities where your DD applies will review her application independently. Of those that make her an offer, she will Firm her top choice and Insure one choice, releasing the others.
Your Insurance is not your second preference. It s the choice where you could get in if you do moderately badly on your exams. I and some experts in the high schools on this Forum advise that the Insurance be two grades below the PGs. So if predicted A star, A A
the Insurance should have a requirement of
AAB.
Sadly, I must emphasise that in a competitive field like Law, meeting the PGs is very far from a guarantee that you will be made an offer.
So I would suggest two aspirational eg Cambridge plus a top London uni or two top London unis, two less competitive London unis or one in London and one elsewhere, and, assuming A star A A predictions. an AAB Insurance offer.
As PP suggested, another good route into Law is to do a different subject at Undergraduate and then a Law Conversion cost. Others will be more expert than me on the pros and cons of that approach.
Very best wishes to you and your very intelligent DD. This will be exciting.