You've met her, you like her, you want to take it a step further, you look into her eyes and say "You are so beautiful."
The question is this: why is this such a good thing to say to a woman? Basically we're congratulating a woman for conforming to a socially determined aesthetic principle -in what way does this make her a good or worthwhile person? Why is this considered one of the highest compliments you can give a woman? You look great in slacks, therefore you deserve to be treated nicely.
To my mind it reflects a social position that places the success of a woman on how good she looks - a variation on the social structure that determines a woman's value by the number of children she has.