Girls, Why does she behave the way when She sees me?

I know a girl who works in a large store near to my university. They offer free tasters of perfumes me and friends would go in and try. Then she comes and asks if we are ok and I said can you pick one out that you like so she pulled out A few but I said what’s your favourite. She pointed it out and my friend tried so I said , wow have to get it now she likes it (suggesting her opinion matters) she laughed and took the compliment.

then everytime I would go in she would always look at me , sometimes we would have a little smile to ourselves kinda nervously. Although I liked her , I didn’t want to go ask her out as it’s her job. But I don’t get why everytime for months she always watching me , and smiling to herself. Then if we up close she acts cold then from a distance she always watching and looking.
then she start coming to my gym, and I could see her talking about me to her friend , now her friends keep looking at me and telling her when I’m about. She always watching me in the gym on her way out and where ever she is. i once asked if she had finished with something and then she was shocked that I kinda Spoke and when I walked off she and her friend kinda giggled.

but why everytime I walk in store , or in the gym she keep looking at me but never speak, and I can see her looking to se where I am say if I move around to different places in the gym. She looked around for me. Why did she giggle like that. Also once she over heard me speaking to my friend saying I think she beautiful an want to ask her out but I nervous to and she was ear wigging and started smiling to herself.
but then she just keep looking , every where she sees me and her friend keep looking
Girls, Why does she behave the way when She sees me?
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