It's true that focusing on
her pupil dilation is counter-productive.
Her pupil size affects
your attraction to her. It doesn't necessarily indicate her attraction to you. The frequency of her pupil dilation can be an indication of what type of partner she's most likely to prefer, though (you'd need more than one encounter to gauge that).
It's
your pupil size that affects her attraction to you and the affect of your pupil size on her will vary.
Dim romantically lit rooms and alcohol cause your eyes to dilate, which will definitely make her more attractive to you and can make you more attractive to her.
There's a lot more variability in the pupil size women desire in any event. Almost all women prefer larger pupils when they're ovulating and most likely to conceive. During the non-fertile times of the month, some women still prefer large pupils and those women tend to have many short term relationships. Some women prefer medium size pupils and those women tend to have stable, longer lasting relationships (they use other criteria, such as intelligence and honesty, to pick their mates). In fact, it's almost as if the best mating strategy for females is to establish a long term relationship with a stable male and have brief sexual affairs with very masculine males when they're most likely to conceive.
Edit: Paragraph deleted, because, actually, her pupil size at some given instant tells you nothing. You'd be better off knowing her menstrual cycle.
If you have small pupils, you're pretty much hosed all the way around. No one likes you because you have 'beady eyes'.
A sexual selection approach to women’s pupil size preferences in a potential mate