She shouldn't try a men's boot. The mens boots would be too tall if she has larger than average calfs. Boots are all about fit. Width of the foot is important. If she has wide feet, Nordicas tend to be wide and Technica has some wide models. If she has narrow feet, Some Salomons are narrow (scarlet, impact) and some Langes are narrow. Langes aren't as narrow as most people think they are. I tried on a lange and it was too wide. The best thing to do is to try boots on at the shop. She should plan to try on a lot of boots in the socks she plans to ski in. Never wear more than one pair of socks. Stiff boots can be made less stiff by a bootfitter, but boots can't be made more stiff. Boots can be made wider, but they can't be made narrower. Her feet should not move at all in the boot, except for wiggling the toes. Even if you decide to buy from backcountry, she should try them on in a shop first. Lower boots would be good for her. Mens boots would not be good for her at all and would cause more pain.