I hadn't noticed that moment before either, DL, but I saw this time that they lingered awhile on Hoffman's face as she "calculated", while Ang and Maggie talked about the dresses before looking them over. Hoff comes to a sly decision, we see that, and leaves just at the right time.
Later, when Maggie tries to blame Hoffman, Alexilique reminds her that Hoffman left before seeing which dresses they were. Oh yes, she answers. Alexis can't be blamed, not knowing the significance of any of them.
It now occurs to me that Hoffman as the servant would have done the actual collecting of the gowns.
I also noticed a big earlier moment of decision in a close up on Hoffman, leading to my picking up on this one. I forget what instigated it, but "Alexis" did something only Angelique would have done-- it was small and subtle, but telling nonetheless. We see Hoffman thinking it over. They spend some camera time on her face, as she does. Then Hoffman brings the voodoo doll and pins to the Room and gives them to Angelique, now absolutely certain she knows who she's dealing with.
I enjoyed that moment, where we figure it out just by watching Hoffman's face, as she silently figures it out. It took me, what, five viewings over many years?