Women's boards typically are a little more flexy than guy's boards due to their lighter bodies.
This. I never understood this. Since people buy boards based on their weight, wouldn't gender not matter? Or is it because for a given guy and girl of the same weight, guys tend to be stronger??
Imho the most important difference is width. If she has large feet, then she'd be okay with a men's board. Otherwise she'd probably be happier on a women's board.