If I can get up the nerve enough, I'll tell her she looks nice. If she thinks I'm a pervert, that's her problem she judges people that way, not mine.
But I'll say this.... if you get what women would consider an attractive guy making a nice comment to her, she'd be more receptive of it, than if he were not so attractive. Then she might think that he's just out for a quick thrill or something.
Guys on the other hand take compliments wherever they can get them.