Triple Bogey said:
I was polite to her, I smiled and said 'hi'. She hated me from the second she saw me. I was there. It was embarrassing. No need for it. Although her attitude has improved a touch since then.
You were polite. Okay, great. That doesn't mean she owed you anything. Why were you nice? To get something from her? I hope not. I'm hoping you were nice because that's just how you are, even regardless of if it's returned. So what, you didn't get an upstanding greeting from a girl you don't know every time she saw you. Brush it off. She may be socially awkward. She may have anxiety around some guys. She might be going through something. You might remind her of someone she doesn't care for, or maybe someone she misses, and she doesn't want to say anything. You never know. You don't even know if she hates you or not. It may be something else entirely.