Your 16, your really into this girl and you want to tell her how beautiful she is before you even see her. Do you really think that she will not be able to tell that you were waiting to tell her that for 4 days? No, she will instantly know that you were just dying to tell her how great she looked and it will not have the effect on her that you hope it will.

What you need to do is keep that line in you pocket and not worry about what your going to say to her when you see her. Why? because you need to be confident that when you actually do see her you will know then that she is beautiful and you will obviously mention it. Don't be worried now that you will screw up what your going to say 4 days from now. When the moment comes you will say exactly what’s on your mind and it will be absolutely genuine and she will adore it just the same.

If you memorize some line now because you are worried that you will screw it up later then it will come out all wrong. Besides, what if in the moment you start to say you pre-planned line and you say the wrong word? Then the gig is up, then it is totally obvious that you planned that line a long time ago. She will then think that your "just saying that to get something' or "you don't really mean it"

Trust me, try to have some confidence and just know that you like her a lot and when the moment comes say the truth that she looks awesome, that’s it. you don't (and shouldn't) tell her how much you are totally thinking about her at this dance. Just have a great time, and she will know that you like her, but not think that you are totally infatuated with her, even if you are.

Good luck