that would be a decent assumption to jump to if you didn't know the real answer i guess...

sorceresses in the Witcher were largely discarded children that were sick or disfigured. they eventually use magic to "fix" their bodies. many of them are obsessive about thiz and use magic to be the most beautiful person in the room because of their disfigured past.

there is very little connection between high birth and being a sorceress in the Witcher. all of the specific examples we hear are of farm peasents being scooped up just to take the burden off their parent's hands.

this is a bleak story, many of the sorcerers and sorceresses in it are at Best morally grey. it is not beyond most of them to take that child and experiment on them if they don't have the aptitude for magic. they are also sterile. much like witchers, they must take in outsiders to propagate.

unless the show has its own lore or something. IDK i stopped watching after season 2 was completely its own story, unrelated to the books at all.