It is possible for a woman to have a "wet dream." I am, in fact, speaking from a semi-creeped-out personal experience.

I was 18 and living with my boyfriend at the time, and I had what I believed to be a healthy sexual life-style.

What I can remember is that I had a very vivid dream, most of which didn't make any sense. I dreamed that I'd gone back to visit people I'd lived with, only now they lived in a medieval castle, and one of my friends who had passed away was there. I came to realize that a man and a woman were chasing me, so I ran away. I came to a tower, and ran up to the top of it. When I got there, I discovered that I was suddenly naked, and the man and woman came into the room. The man stood at the top of the stairs while the woman came up to me. I was backed into a corner, and she put her mouth on my "nether regions." At the same time, I felt an incredible amount of pleasure all at once, as if I'd had an instant orgasm. Being a decidedly straight young woman, not having any feelings of that sort for women at all, this shocked me, and I woke up thinking that it could only have been brought on by my partner coming to bed. Upon waking I found that I was still alone in bed and passed it off, going straight back to sleep.

It's been 2 years since then, and I've not had another before or since. As someone who normally has a shockingly bad memory, and can't remember dreams for more than a few hours (unless they were nightmares), I suppose it shows how much of an impact it had upon me.

I apologize for the long walls of text, but I hope this can help other young women understand dreams a little better.