Generally, you need 1-3" of standover clearance when you stand with your feet on the ground. What size this translates to varies, since the lower end of the seat tube (at the bottom bracket/pedally end) varies in height off the ground.
Have a look at the websites of Trek , Canondale, also Bianchi, Terry, Jamis and Wylder.
They have womens bikes in their range. These should come with small frame, fitted with small wheels (650c rather than 700c), short pedal cranks (160-165mm) and narrow handlebars (38-40cm), ie a smaller bike, not just a squashed down large bike.
What kind of riding do you want to do? Racing, fitness, touring, commuting. Most of the quality womens bikes are really for racing and fitness.