As a germanic name it has initial stress. I'm not sure about the pronounciation of the letter z, but for a high german name it will be /ts/. The letter e is either a clean /e/ sound (like in bed) or a shwa. So my best gues is AH-ve-tsa.
It is a diminutive form of
Ava (Frau
Ava is the first female poet in german language known by name, BTW).