Confused about my relationship (does she like him or me, is she using me)?

So for starters.. I'm a 15 year old girl. Just saying it so you know lol And this other girl, who's one of my best friends, told me she liked me, and now we're together. That happened a few weeks ago. Now, we're pretty close i guess. But it was the homecoming game tonight.. We had fun at first, but then she wanted me to come hang out with her and this boy. I was TOTALLY fine with that, because they are pretty good friends, and i am friends with him as well. But when we were hanging out with them, they were barely talking to me at all. So then i went back to my other friends for a while. She came back a minute later, but only to take me back to the guy. I said i didn't want to, so she stayed with me for a while. I was SUPER cold, so she was snuggling with me for a minute. After that, she went back to the boy at halftime. She didn't come back until the end of the game, and she wouldn't stop smiling and talking about him. I don't get it. She obviously likes him.... but she said she likes me a lot. What's going on, and what should i do?