Formica pallidefulva have quite cryptic nesting habits, which makes things difficult. They don’t build large mounds like fusca group formica. However, if you have lots of formica subsericea or any other fusca group formica in your area, there is a chance that this is a rufescens-breviceps group polyergus species, which target fusca group species and not pallidefulva group species. P. breviceps has lots of records near your area, which makes this more likely.
here are the other pictures i took of her. unfortunately all pics come from my phone and my shaky hands, so quality will always be a little questionable. you got me nervous now, i'm a first year ant keeper and the discord i'm in says this can be a difficult species to keep. i don't want to be offering my 2 queens the wrong workers. i actually considered letting one of them go and follow it around and see where she will take me.
here is a solution: offer one queen formica subsericea workers and the other formica pallidefulva workers. That way, at least one queen has the right host species. Also, i would use callow workers, as they quickly bond with the queen and will feed her.