So confused, does she like me?

So.. there's this girl that I like, I only started talking to her around 3 weeks ago, but I went to school with her for six years before hand. She's the type of girl that always has guys chasing her, and could probably get any guy she wanted, that's why I never really spoke to her back in school because I didn't have the confidence to talk to girls like that.. but recently Iv'e been going to these after school maths cles (I failed my exam) and it turns out she goes to, on the first lesson I lent her my phone because we were all pretty bored, and she put her number in it, I started texting her, and spoke to her on facebook, and MSN.. but she doesn't seem too interested (usually gives me one word answers) she's told me that she thinks that i'm really 'fit' and a really nice guy, and just the other night some girl was trying to start an arguement with me over something stupid and I just said I cba to argue, and then she said "I wish I had a boyfriend, that didn't argue with me". The main reason I question whether or not she likes me is because she still talks and texts her ex a lot, and loads of people keep saying that there still not over each other.. what do you guys make of it? Does she like me? Or is it just harmless flirting? all answers are appreciated, thanks!