Not an expert myself, but I can see that the proportions are slightly off. The distance from the Eye to the lips, and the chin is a little too much. And also, you want more rounded, curvy feel to it in order to make it look more
feminine. Now some women have masculine jaws and still strike as beautiful (Olivia Wilde for instance). So its really about looking at references. A lot of them. But before that you want to decide what genre you are going with this.
Cartoony? Realistic? Stylized etc. That should help you narrow your references down. But in general, I would say bring the jaws in, pull the chin up, and work more on the eyes (the temporal line is a little too prominent for a woman).
Hope that helps a bit.
Cheers.
P.S: There is a tool in zbrush with a skull in it. Append it to this one, and keep checking the proportions as you work with the sculpt.