about 200cm by 200cm minimum with 2 basking, 2 uvb and 2 rest spot (to avoid competition for the "best territory" and there is no warranty at all, sometime ti work sometime no, I house all my melleri together in a freerange (well.. I got 3 (2 female 1 male) the space of the freerange is about 550cmx550cmx400 and they found a way to fight (no real fight.. just some "get away from my place")
Your girl look dehydrated and sick too, did she eat? they all are wc? she have a laying bin (belly look a bit big too me and nails are super sharp.. maybe she just carrying egg and getting egg bounded.. if its the case she will never lay in front of the other and need privacy ?
So with no doubt now you should house this girl separately with laying bin no waterfall, good misting, a fogger at night, good uvb and some peace.
that way you will be able to track the poop too.. but can you still describe me last poop (any adult poop on the cage) this can reveal parasite presence or dehydratation