Ball python tub

A 28 is perfectly fine for her. I give my adult males about that sized tubs. The only reason I give my adult females 41 qt tubs is so they can thermoregulate as much as they need to. I don't use any hides except for my babies, but it sounds like you don't have a rack system, just a tub right? In that case I would give her a hide or two and put some fake plants in or crumpled newspaper to fill up the empty space.

Personally the plan I follow is 12qt up to 400-500g, then 28qt up to 1500g, then 41qt for adult breeding size females. When I have some neonates, they'll probably go in 6qts until they sell or reach 150g.

I use the 41qt for my girls and with them I have a hide on the hotside and one of those large plastic dog water dishes on the cold side. All of my snakes squish themselves under the water bowls so it acts as another hide. For the boys I go to 32qt. And they don't have the hide. But don't seem to mind. They still have the same dish so they move that around at will and squish underneath it.