Say, “If girls were boogers, I’d pick you first.” Saw this online, probably would make the girls go bananas for you.
Here's something that I did. Some find it over the top, but I think it's perfect. Take a deck of 52 cards, and for each card write a reason why you like that person. Thinking of 52 reasons may be tough, so you could use something like this deviant art post for inspiration. https://hazel-almonds.deviantart.com/art/365-Things-I-Love-About-You-162213659 That, and her favorite chocolates.