You don't have to spend a lot on a separate enclosure.

Shopping list:

• 15qt Tub (or some sort of plastic latching tub of a similar size)
• SMALL heat pad
• A Thermostat or Rheostat of some variety. This is a MUST to control temperature. Get a probe digital thermometer or heat gun to make sure your temperatures are on point. Analog (aka dial) thermometers are crap and not accurate.
• Go to a hardware store that sells flooring tiles, see if they have a damaged tile of some sort that they'll give you or just buy something cheap. You'll be sticking the heat pad to this, not directly to the plastic tub.
• Paper towel for substrate
• Hide and water bowl

Final product will look something like THIS.

Put a couple small holes in the side of the plastic tub for air flow using a drill or solder iron or something.

She needs a humid environment right now, moisten the paper towels and make sure she has fresh water.

If you need to, put her somewhere dark or throw a towel over her tub. She sounds stressed.

As others have mentioned, do not house multiple ball pythons together. They are competing for resources and she is showing signs of obvious stress (not eating, lethargic, etc). Humidity requirements are not on point since she doesn't seem to be shedding well and she looks dehydrated. I would recommend a tub for your other snake, too, but our main focus is her right now.

Get her to an exotics vet and see what they say. The main thing is to get her stress down so she will get back on food. If she is sick with a respiratory infection or something, she will need to be treated by a vet.

Best of luck with her, let me know if you have any questions or need any clarification on anything.