From the clients I have trained, and the bodybuilders and fitness women that I know I can tell you this:

Women look fit and very good (read: feminine) at 17% to 20%. You can get outlines of your abs at that percentage, depending on how your body deposited fat to your frame.

For a woman to get "ripped" (six pack, very clear definition) you are looking at 13% and below.

Again, that is a very different thing for different people. Some can handle it and have no problems getting down to 10%.