Kraj said:This is definitely a risk you take, but she won't buy the explanation you came up with and it'll make things worse. Go for self-deprication instead: "I can't believe I didn't notice until now. What's wrong with me?" followed by a follow-up compliment: "You look so beautiful." Getting frisky at that point probably won't get you sex but it'll convince her your not b.s.ing.
Oh, hell yes, ask! When you ask if she's changed something and she says no, you just follow up with, "Wow, you just look so good today I could have sworn you changed your hair (or did any other type of thing to look extra good)". This tactic is 100% guaranteed golden; if you're right you noticed something she did; if you're wrong then you're paying extra attention to her for no reason at all. Either way you're noticing her and that will make her happy. The only way you can screw this angle up is if you're obviously full of it.
Ok guys, we may have found a way to cheat here by taking Kraj's advice. Kind of like looking in the back of the book to get the answers