How to open up to an old friend?

I love this girl. I love this girl so much, (Bruno Mars's "Grenade" Song sums up my passion x1000), and the thing is, we're child freinds since Preschool. I Liked her as a friend, but i was always a spazzy, talkative, little runt. I was always doing stupid stuff as a kid, and acting weird, like punching gurls, and pushing them. But i was 5. Now im 16. I havnt seen her since i was 10. I try to talk to her on Facebook. the thing is, everytime i talk, she only talks about ACT, school, Pharmacy (Her dream Profession, and ironically, mine as well). and noodles. Our convo's are bland, and such a chore to talk to. I cant flirt with my barber and she' 25 (She though i wass an older man). I turned down 2 of my friends when they asked me out. just for her sake. Idk how to sum this up. but iv been thru alot for her, for the past 5 years. and she still thinks im the little runt from 5 years ago. i need to tell i changed. but i cant put in words for her, or make her know i love her. i just want her think we are firnds, and thats all. Thank you.