I could argue that girls aren't purposely confusing, but I'm not 100% positive that that would be the truth. I think girls can easily become manipulative and when they get things in their heads, and they know exactly what to say to the people around them to achieve desired effects, then it's only expected that whoever they are trying to manipulate gets confused. Confused yet?
Girls can make someone confused (and that's anyone, not just guys), to get what they want. But to be honest, I think this particular scenario works both ways.