I had exactly the same when I was at work and I never knew why. She could be downright rude, let the door go in my face even though she saw me coming. I just decided she wasn't worth bothering about. I was always civil to her and if she couldn't be the same that was her problem. When she got married there were whispered huddles sorting out presents, others didn't want to upset me as only myself and another colleague weren't invited. She was upset by it - I wouldn't have wanted to go anyway and didn't contribute.
You can't like everyone you work with but that shouldn't stop you being civil and courteous - she was neither.
How do you acknowledge Easter.
Is it me or am I getting mixed messages