Many vets will tend to lump all reptiles together into one broad category and make the same assumptions about them all. It's true that for MANY reptiles, UVB is essential to thrive. But for many, it is not. Ball Pythons are essentially nocturnal creatures who spend their days asleep in dark dens and come out after sunset. They're not getting UVB in the wild, so they don't need it supplemented in captivity.

I'd look for another vet...but I wouldn't despise one for not being an expert on all reptile species. At least she was willing to try and maybe will be spurred on to learn more someday.