I will tell you what I have found so far in my year and a half of riding.
There ARE seats that are more comfortable for a woman's anatomy. It depends on her build and how aggressive she rides. If you go to a bike shop, they know exactly what would be best for her.
No, I do not wear anything under my bike shorts. That would cause chafing and more moisture. Buy a good pair of bike shorts (made by Trek, Izumi Pearl, etc) with a good chamois and that will really protect the "area". There are shorts made specifically for women and they have saved my butt (literally!) :-)
Hope I am able to help.