Is this CRAZY i really like this girl in my group of friends?

i met thes girl last year at College i knew who she was all year and hung around her but we never seemed to click. then with like a month left before summer it started to feel like she was Beginning to like me i always made her laugh, we would pick on each other but in a flirtatious way, and once the one time i could not make it to the weekly thing we both went to she wrote on my wall about why i wasnt there. we found out we are both going to a concert in a week and are planning to hang out. i guess i just cant tell if shes flirting cause thats what she likes to do or if she likes me and if i ask her out will it hurt our friend ship if she says no?. any advice?