Physiologically, when a woman is aroused, something will happen that it analogous to an erection in a man-- blood will flow to her genitals, causing some swelling, especially in the clitoris, which is made of similar tissue to the penis. This will be more or less noticable depending on how prominent the woman's clitoris is (it varies). In addition, the vagina will lubricate, as the body's natural preparation for penetration. Different women will produce different amounts of lubrication, and it can also vary quite a bit for individual women.

Women who aren't heterosexual, fori instance, are not likely to want intercourse when they feel a libido surge. Women who enjoy other sexual activities more than intercourse also aren't. And for plenty of people, the physical sexual drive doesn't equal the emotional one: in other words, the drive is generally just for release, which masturbation handles nicely, and when it is nothing but physical, is ideal since using people as sex toys isn't so cool.