After all, there are so many hurdles and nuances that you need to avoid when it comes down to it.
If you don't show enough, she might pass you by because she might feel like you're hiding something.
Actually, there are a couple reasons for having more then one clear close up (main- photo-worthy) photo.
The girl who didn't click your profile when using one photo, may click it when using a different photo.
So you're going to be mixing it up among a few main photos.
They say that a picture is worth a thousand words...