I've never read the books, but... It was clear from game 3 that she was going to play an important role in the future. The entire plot of the main campaign in Witcher 3 was about HER powers. The Wild Hunt wanted her, not Geralt.
Plus also she's awesome anyway. What the fuck is wrong with people? Oh I can't enjoy my vibeo game with a wahmen as main character, it'll ruin my mood!
Honestly I'd rather be looking at a cute girl dashing around than an old man, even if I identify more with the latter. Video games are for exploring things. Fantasy worlds, dragons, wraiths... And the biggest problem with suspending disbelief is playing a character who isn't the same gender as the player? lmao.
Maybe I'm just not enough of a gamer. Only been two and a half decades or so since I first touched a computer and played games.