There are lots of good choices out there these days. A number of bootmakers now have one model or another of a "winter sports" shoe or boot, usually a slightly relaxed boot with insulation, waterproofing, and other winter-friendly features.
A really good example is the Columbia Sportswear BugaTrek Omni-Heat ($100), a pair of which I just purchased as a winter dog-walking/car-chain-installing/hiking boot. They're great boots, sort of light hikers with a winter touch. They have both Thinsulate insulation and Columbia's proprietary Omni-Heat system, which is claimed to reflect heat back into the boot (they're warm, that's for sure). Grippy outsoles and a fairly beefy nylon shank round out the picture. They look nice, too.
Another good winter shoe is the Garmont Momentum Snow GTX ($140). They're pretty heavily insulated with Thinsulate, and have a Gore-Tex bootie to ward off moisture. A bit more technical-looking than then BugaTrek. They'd work very well with snowshoes.
Lastly, a really interesting show is Salomon's Deemax 2 Dry Winter Boots ($140). These have upper made of a polyester soft shell material that is weather-resistant, very light, and breathable. They're also built on a women's last, not just re-sized for women. So fit would be great, and comfort as well. Maybe not quite as warm as the other two, but very athletic.