There are all great schools, I agree. The whole offer/waitlist thing seems to change from year to year, depending mostly on who you talk to! Last year there was an extensive thread where parents were being offered StCats and waitlisted at Priorsfield. But then that was in the midst of StCats PR disaster surrounding its dire pandemic response. But, it's just impossible to know what's going on, especially via forum. Theres also an extensive thread of current parents moaning about 'current' issues at StCats, however, like the PP, some say it is 'historic'. Again, the danger of the forum environment is that we don't really know what is gospel, what is experience based opinion or what is simply made up/exaggerated.
The only real fact to note, if you're looking for a school in Guildford for your DD, is that you have some great choices, that all perform well academically, yet offer different (but generally very good!) learning experiences. The fact is you will need to get out there and visit them for yourself to actually discover which one works for you/DD.
There is a real need for a co-ed school in Guildford, not sure any of the girl's schools will jump on it though. Until the supply of girls willing to apply starts to dry up, why bother? Looking at the inspection reports, Tormead which you mention, has actually grown over the last 3 years, and I'm sure they are still maintaining their high standards, as diluting the intelligence level of their cohorts would be counterproductive. As just one example, a friend's daughter went to Tormead's 11+ activity day and counted way over 200 kids, and assuming they didn't all go to the optional event, there is clearly still a healthy supply of interest in a girls only education in/around Guildford. Theres also another post on a facebook group I'm in for Guildford Mummies, with someone saying they're on the waitlist for Tormead Reception as its completely full, asking for alternatives - amongst the suggestions was StCats and Rydes Hill - again both good girls' schools! So another indication that the girl's schools in the area must still be attracting interest, at the younger ages too. I do feel that this appeal in a girls only education has grown massively in the last 2 years, especially with the whole drama around the me-too movement, etc. I was great believer in mixed education, but I too can see the benefits these days.
OP, I would highly suggest you go look around, take advantage of the in-person tours that are becoming available and ask some questions. Tours tend to be during the school day too, so you'll be able to see all these four great schools in operation and decide which one is the 'fit' for you.