I think what we're getting at here is that we like a girl who is smart or intelligent enough to bring out the best in us. If a girl is too easy, then it doesn't really inspire you; it doesn't feel as meaningful. However, if the girl plays too many games, then you get a headache and it's over (either you move on or you fall for her tactics).
I believe the solution is just doing what you want to do and listen to your gut. Usually if something is up, your gut will tell you. If she wants you to go fetch her something, why would you obey? You two aren't dating! At this point you owe her nothing! Of course, decline in a C+F way.