Girl's Behavior

She's quiet around me but stares at me from a distance?

This female co-worker of mine has got me all confused everytime I'm alone with her she is quiet and reserved I usually initiate the conversation but the thing is she is a very opinionated and outspoken person in the office the only time she talks to me is when other people around and it's usually small talk like how's the weather what are you eating for lunch stuff like that I don't get that at all and on two occasions I seen her looking at me from a distance the first time I'm not conclusively sure if she was looking at me specifically, however using my peripheral vision she did turn her head towards my direction for about 6 to 7 seconds and turned back but the second time though I CAUGHT HER LOOKING!! I was talking to this other female co-worker when a person came from behind me going towards the door I knew someone was going to the door using my peripheral vision but I didn't know who it specifically was cause I was in the middle of a conversation but anyway that person before going out the door decided to stop and turn in my direction and stood there for a good 4 to 5 seconds. At this point as I'm listening to this other person talk in my head I'm like who the hell stops and turns before leaving out the door so I look towards the door to see who it was and it was HER!!! And as soon as our eyes met she turned towards the door and walked out so what gives? Any clue why she acts this way
She's quiet around me but stares at me from a distance?
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