Fit your boots to your bindings to make sure they are a good match up.
Really, the flex in most women's bindings is pretty similar, so you're going to be looking more for comfort and functionality. Look for bindings that have comfortable straps and ratchets that slide easily. Don't buy the cheapest binding in any line-up.
I love love love my Rome Madisons.
Lots of love for : Burton Escapade, Union Trilogy, Flux GU30, K2 Auto Agogo