Is my gf embarrassed of me?

hi today was the last day of school... and im in the drum line which had a performance in the auditorium, so i see my gf in the front row while we were playin and i smile at her and she starts turnin red and smiling and turns to her sister and they both look at me and start gigglin... what could i have done... we're both 15 PLZ HELP!!!!!