The bruxa Geralt encountered and killed in self-defense at Corvo Bianco differed from other creatures of this sort. Firstly, it was more intelligent, capable even of articulating words in human language without much difficulty. What's more, this bruxa was tied to the Beast, the mysterious murderer prowling Beauclair at the time.
Fighting it presented Geralt with quite the challenge. Like other bruxae, this one possessed strength and speed far above that of any human, could turn invisible and could attack using a sonic wave.
As is typical for all vampires, it sought to suck its victim's blood. This meant the usual defense against those creatures, the Black Blood potion, was an effective weapon against it, as were the Moon Dust bomb and, naturally, the witcher's trusty silver blade.