I'm pretty sure the whole thing is that witches in the witcher universe can shape their faces however they want so they all choose to be super pretty? Am I misremembering or did yennefer make herself "not conventionally beautiful" on purpose?
“Unlike priestesses and druidesses, who only unwillingly took ugly or crippled girls, sorcerers took anyone who showed evidence of a predisposition. If the child passes the first years of training, magic entered into the equation – straightening and evening out legs, repairing bones which had badly knitted, patching harelips, removing scars, birthmarks and pox scars. The young sorceress would become attractive because the prestige of her profession demanded it.”
This is just another way in which the TV show butchered the original, although it is far below the ladder in comparison with the fact that they turned the endless interesting philosophical debates into dull, uninteresting conversations.