Congratulations to your girls (and you!) on all the G&L interviews. I'm afraid I don't know how many they interview, but there are about 110 in a year (5 form classes). It is a fantastic school - academically and pastorally.
I think when people talk about groups from different schools being called to interview, they don't mean girls were actually interviewed in these groups, but that applicants from certain schools or 'centre groups' tend to get the same time slot. But they are all interviewed separately! When DD went (just pre-Covid) there were 4 or 5 other girls from her school and all were offered places.
I think they had 2 interviews, each with a different teacher. The first was a kind of general chat about favourite subjects etc. They did ask what other schools they were going for and they asked DD if she had an interview at SPGS (which I remember thinking was s bit odd). Then the second interview was about some pictures (but they all had a different set of pictures).
Many of the girls offered places at G&L had also sat for FHSS and were offered scholarships there. It said in the FHSS offer letters that they were among the highest performers in the Consortium. So well done to your DDs today!