A girl keeps saying hi to me every time she saw me?

I am a 8th grader. A girl, she's pretty. She keeps saying "Hi" and smile at me every time she saw me walking in the hallway. I didn't mind the first few times, but its been almost three weeks. I don't know what to reply, so just say "Hi" back. We are not close friend, I have class with her once a day (not much) She asked me about where I live, what I like...

Today, she ask me, "Hi... Forgive me if I'm wrong... Are you gay?" I was scare, because I didn't even think I like boys and I didn't think I look like I am gay. I told her no and she said. "Oh... Never mind... Y ur cool. Bye" with a smile.

Also, my friend told me something at the beginning of the school year that she likes me. I was looking at her and she immediately said. no no... Don't Listen to him. I was fine with that, cause I knew they are joking around. But what's more strange is that she was waiting outside the school til I am going home and explain that others were joking and don't listen to them. Okay, and I didn't pay much attention to those thing.

Now, I am guessing that she likes me, but I am really not interested in have girlfriend in middle school. But honestly, she is really pretty and nice. I don't mean that I love her, but... Just asking.