One of the obvious things would be gearing; lower gearing to make hill climbing easier. It's been pointed out to me that changing out a cassette is pretty easy meaning you could have one with lower gearing for hills and another with higher gearing for flats and speed. From what I can see it's an easy, 5 minute task to do the switch (see
link) I know some of the girls here have done it.
A second possibility is that you probably wouldn't want a bike with a longer wheel base; those are mostly designed for comfort on the flats.