How to tell if this chick likes me?

Im a freshman and this sophmore girl that goes to my school sent me an invite on FB. I accepted it and she started talking to me on chat. She asked me how old i was and asked me how i felt about a 15 and 16 year old going out. I said it was fine, but i asked if she was messin' around and she said yea. But then she started flirting with me a little, calling me cute and handsome and all that. Like a day later she sent me a relationship request, and i don't even know this girl. I asked her about it on Fb and she asked me what i thought about it. what does this mean? is she testing me or something. Im 15 and shes 16 btw, and shes kinda hot. The prob is that i don't know this chick and im a pretty quiet guy.