Take a look at Northwave shoes. I absolutely LOVE my women's Northwave Velvet SBS road shoes...wide in the toe box, narrower in the heel...perfect! I'm not sure what Northwave carries in the way of women's MTB shoes, but if you are even thinking about switching over to road shoes, I would definitely recommend checking out the Northwave line. This is the shoe I'm currently wearing -

http://www.realcyclist.com/roadbike/.../NTW0033M.html