Mei can use that jutsu too. And she can cover herself with acid mist. If Zabuza approches to her she just melts him.
Not if it's a Water Clone, which is how Zabuza will get the idea to not move so close to her and to use his Suiton techs, such as Giant Vortex Jutsu, which she wont be able to sense and avoid because she is hidden in the mist.
Mei doesnt know Silent Killing, the only reason she used mist the only time was to avoid Madara's Sharingan, thats it, she cant locate anything with sound alone like Zabuza. So Mei would then get swooped away with the Vortex, and it will leave her defenseless because it took out Zabuza, the guy who could with stand a dozen swords impaled in him while still fighting full force with a kunai in his mouth. That being said, it is evident Zabuza is just physically stronger. So once she's defenseless, Zabuza can just blitz behind her and use Water Prison Jutsu, then its game over. Zabuza solos.