I agree she likely had a place she carried several phones with her. However, this is how many people end up getting burned using burner phones.
They drop their personal phone in the pocket, bag or holster right next to the burner phone. Police doing investigation discover a strange number, that number has cellular data attached to it, just not the name of the person using it. However with cross referencing the suspects personal phone data the trail of the ping on their personal phone matches, and boom you are implicated as the one controlling the burner.
It has not been released to the public, but I would expect that police required KK to provide the cell numbers on her burner phones, so I am sure they pulled what records exist. (I know tower pings are erased after a short period, but there is data from no connects and other interactions.)
The burner numbers would have shown on PF's cell records too, unless he was using a burner. Once again KK would have that number and those records would be collected.
I am expecting the cell data from all of the phones will be one area that is expanded significantly from the rudimentary level of discussion done at the preliminary hearing, where it only concerned the phones of PF, KK and KB. Especially considering the acknowledge the use of burner phones.
MOO of course, since my wife refuses to share my opinion.