Like other prey animals, guinea pigs appreciate being given places to hide. Poof made good use of this makeshift tent by camping out behind the flap, eyeing other pigs as they approached her hiding spot. You could see her projecting, "Back off, this is alpha pig territory!"
Jazz up your cage with a cabana or two - it's as easy as draping an extra bit of fleece or other cloth over a corner and binder clipping it into place. Allow the sides to hang down for added pig privacy.
We can't see you at all, Poof!