Matt-
Simms tend to run a tad bigger then the Patagonias (especially if you go with the Guide or G3 as they have a much more pronounced articulated knee).

Another thing to consider is that most women fit men's waders as well, if not better, then women sized waders.

She may want to try a Small King (which they only make in the Guide and G3), Medium Short (again, only Guide and G3) or a straight Medium which they make in the Freestone, Lightweight, Guide and G3.

If you give me her height and other relative measurements, I can probably nail down what size she needs.

I own a pair of the Guides, G3's and Patagonias and each has its pros and cons...I have never worn the Lightweights nor the Freestones but I have sold I dont know how many countless pairs of the Lightweights and have only seen 1 pair come back due to leakage.

Since the Freestone's were introduced at the first of the year, I have sold a good number of these as well and have yet to see a pair come back.