I don't think that women looking "flirty" is attractive.
But they are more attractive - for the same reason that women wearing short skirts are more attractive and it may not be for the same reason you think it is.
The reason has to do with accessibility: women, unlike men, are very picky when it comes to dating. We (men) know this and when a woman doesn't look like she's looking for men, we often choke or don't bother pursuing a date. A flirty attitude is the strongest indication that a woman is interested.
Looks more predatory to me
Some people, men or women alike, often end up with dumb looks in photos :: that's what happens when wanting to simulate sensuality when you're not in the mood, not to mention some people are just not photogenic and really need the help of an expert for such photos. I am talking about genuine sexy looks above, not "
let me eat your brain" looks :)