The only difference between a good girl and a bad girl, is that good girls are very selective with who they're bad with. If my darkest secret is how naughty I can be then I pick wisely. They tend to fall hard.
Check out this great illustration featuring the DC Comics vixens. The illustration is called "Bad Girls," and it was done by Mimi Yoon. This is her rendition of Harley Quinn, Catwoman, Poison Ivy, and Talia.