Well to start, if your going into more parkish features then a high back with more flex for freedom is what you want, if your going to bomb hills/shred pow then a stiffer high back for more precise control. For you, id think probably suggest an mid flex one for all mountain. But i don't know a whole lot about womens equipment so thats just general. The most important thing though, get bindings that fit and match the boot. And don't cheap out and get the cheapest bindings you can find. Varying on the bindings you'l regret it.
Hope that helps you.
Sorry if there is any mistakes in this, i'm pretty tired right now.