<human>: Can you give me the gist of the text in a nutshell?

So when I was about 15 with no car, no job and no relationship experience this girl who I kinda liked, not extremely sure, was flirting with me. 

I was fairly certain she liked me at the time, but not completely sure. I didn't act on it because frankly I wasn't sure myself, and 15 year olds with no job or car shouldn't be "dating."

Around April of that year she told me she liked me. Nothing direct but using hand motions and mouthing the words. I ignored it hoping soon enough it would die down. About 2 or 3 weeks after that she started going out with another guy, a good friend of mine. Not a big deal and rather irrelevant, but still. I thought this proved that she simply moved on rather quickly. 

So that was about two years ago, and I figured the feeling had long since died. She is now going out with a new guy. He is nice and I like him a lot. He's a good guy. But whenever he isn't around she flirts with me. So I know the feeling is somewhat still active. 

Any advice as to what I should do? Is it normal for girls to do this? Do you think this is just an attention grab?
<bot>: Girl likes me, but has a boyfriend. Flirts with me when he's not around. What should I do?