Does she think I'm an asshole?

Ok so I work with this girl I had a bit of a fling with when we first met, and we kinda fell out as friends but we are civil at work, shes always polite. I try to be more friendly/banter with her more than she does with me/I intitate nearly all conversations.

I was talking to her about a friend at college, and how he had told some girl she was stupid, (because I found the story funny). Then she asked me "Well what had he said or done to her before to make him say something like that"

I was a bit confused about her question so I just said "Nothing he was just telling her the comment se made was stupid" and I was laughing a bit when telling her this, then she just got up and said "mhmm" and started walking away. (we had just finished taking stuff out of our lockers)

One other time she was stocking the area of the shop with another which I was set to do, so I said to her "you guys are too kind" and then she said "Well the supervisor asked me to do this, I'm not doing it out of the kindness of my heart" so I just said "well it's still nice of you"

Why did she react like that?