Why was this girl weird with me?

I was a resident assistant in college. I had a supervisor who was pretty cool at first, but changed towards me ever since I didn’t want her to take me to the store on day because I already had a ride lined up with my friend. She kept telling me that she doesn’t mind, but I kept saying no (she was pushy). Another time was when we had freshman move in day, and the RAs and football team was helping the freshman move in. I was helping, and over extending myself to the point where the football players were telling me to “take a break”( i was an athletic trainer for the team and the day before I had passed out cause of the heat) . She over heard, and questioning about me, asking me why I never told her this. After the day ended I sat down with her and told her that I’m a private person and when I say I’m fine then that’s what that means. She said the she was just making sure I’m ok and shell be here when I need her. (Again, pushy) She “understood”
Around this time she had a problem with another RA, and they actually got into it in front of the freshman. she and the RA did not like each other at all. She then told the RA that she scheduled a meeting with the manager and I was supposed to be there as well. (Because I left a book out the office and forgot to put it back.) that was totally unfair to me because I thought “me and you never got into it so why am I going to this “serious” meeting? In the meeting I explained to the manager what I did was a mistake and never had a problem with the supervisor , but it didn’t matter. ( the supervisor and manager was really close) The supervisor was sitting in the room having a smirk on her face. The other RA and I both got written up.
after that I just stay away from her At this time , she was being friendly and saying hey all the time. I’ll say hi but not enthusiastic. She still didn’t like this and eventually got me fired. even after I was fired I still stayed in the freshman dorm, and she still wouldn’t leave me alone. Why?

Why was this girl weird with me?
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