Got a problem with my BP =/

A lot of ball pythons have problems adjusting to enclosure changes but I'd expect this one definitely would. She's 2.5 years old, so she's an adult. She's gone from a racking situation at a breeders to a huge open glass enclosure. She's an adult whose only known one way of being and suddenly pretty much every single thing in her life has changed overnight. She's also with someone unexperienced in her species so that's not easy on you or that snake.

My best advice is get her into that rack and that tub as soon as you can. Leave her a minimum of 2 weeks with NO handling, NO atttempts to feed, NO interactions other than to remove waste product or freshen her water or bedding. After that time period introduce one live rat pup and then walk away. The pup can't do her any real harm and should hopefully trigger her hunting instincts.

As far as her belly, was that mark there when you got her from the breeder? If it's developed in the 3 weeks you've owned her then you need to check your temps, check that your substrate is not wet from spilled water or her passing urine, check that if you are using underbelly heat that it's being controlled by a tstat so it isn't spiking. If it's not too bad, I'd suggest you apply a bit of triple antibiotic (without the pain reliever in it) and put her on plain white paper towel layers as her substrate until her belly is completely healed. If it is bad or is spreading, see a vet immediately.