In my experience, if a girl really likes you, she'll do the pursuing. Right now I have a girl that's pursuing me very heavily, and I'm not that interested in her. I'm not even leading her on, and I'm not even flirting with her, but she is coming on super strong.
On the flip side, I've also known girls who are not that interested, the behavior corresponds.
The key to realize is that you can't come on strong to a girl who isn't giving you clear buying signals or just making it clear that she's into you, otherwise you'll get nowhere. Girls are more aggressive than they get credit for. If they like you, you'll know it somehow.
Forget about wasting your time trying to raise IL in some girl. I agree with IRONMAN22 that there are so many women out there, don't waste your time on one that isn't into you.