[jamesaguilar]

Maybe because neither of those words connote vapidity?

[sliverstorm]

What's the feminine alternative to "dude"?

[jamesaguilar]

None that occur to me off the top of my head, at least not when speaking about someone negatively. You could always go full-ninja-turtles and call her a dudette. Chick certainly isn't it, though.

[paulrademacher]

According to wikipedia, either "dudette" or "dudess."

http://en.wikipedia.org/wiki/Dude