Girls, why does she act this way with me?

At university whenever I walk around campus I would see this girl. I didn’t know her or anything but for some reason she would always make eye contact when passing or stare at me. I thought she was cute. But just couldnt understand why she would always make the eye contact or stare.
recently I accidentally followed her on Instagram. She followed me back. We began talking some time after. And spoke about what we study etc. I told her I though she was hot, she said thank you but warned me she had a boyfriend which I respected. I told her if the situation changes then I want to take her out. She said “thank you xx” but followed me on her other accounts , and now we keep talking , she keeps putting loads of “x” kisses after I said I want to take her out. And yeah congratulated her for passing exams. And she keep talking about future plans etc. Just not sure why she keep putting “x” ever since I said she hot and want to take her out. She doesn’t know me and she even said she has a boyfriend. Why would she start putting “x” after she said she had a boyfriend and after I said she’s hot and want to take her out sometime.
Girls, why does she act this way with me?
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