My most recent (and the only non secondhand bike I own. not surprisingly given the cost) is a Roberts and they told me when measuring me up that it's not always true that women have longer legs in relation to overall height...
On average women do have longer legs, and shorter torsos than men, however that doesn't mean that you don't get long legged men, and short legged women. They are just less likely.
This does mean that since most off the peg frames are designed for average body shapes, a frame intended for a woman ought to have a shorter reach for the same frame "size" as a mans. Of course, since there are a lot more "mens" frames out there, than womens, women often end up compromising with that sort of frame shape. If your proportion are more "average man"-wise, that's probably an advantage, unless you're small as well, since men tend to be larger... on average!
Of course, in a ideal world, we all get custom frames made.
