Guy's Behavior

Girls, would you get upset if a guy didn't say hi to you?

Well, I've been talking to this girl for about 6 months. I want to date her but sometimes I get the feeling she doesn't like me much, but others I feel she wants me but doesn't want to admit it. Recently I went on vacation for a week and when I got back I saw her and since we were on a "down" period (we argued and we weren't talking before I left) I didn't really feel the necessity to be too friendly. She saw me and said hi and I just said "hey, what's up" and continued walking. Later I went up to her and she was in a bad mood because she was giving me one word answers. I asked what was wrong and she told me that she said hi to me and I ignored her. I didn't really ignored her since I did say "whats up" and that's usually the answer I get when she is "mad" at me (or sometimes she doesn't even say hi at all and if she does, its usually not as WARM as the greetings she gives to others, with names and everything, she never says my name). Would you get hurt if a guy said "whats up" to you? Why did she get upset? Was she expecting something more maybe? I've never had a girl get like that over a greeting.
Girls, would you get upset if a guy didn't say hi to you?
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