Girls, Why whenever she walks passed me she keep looking to the ground smiling?

I noticed she keeps looking at me in the gym. Sometimes she smiles to herself when I’m around. She was getting personal trained by my friend and he said she kept looking at me and smiling to herself whilst he was trying to train her. He got jealous because he liked her ( I never spoke to her) then I saw her in a local store with a child and she walked passed me and smiled. I saw her again in the gym on her own. She kind of looked again and tried to smile. A guy I believe to be her boyfriend because he picked up her car keys was walking up to her. She kept staring at me, when I walked off. She keeps walking passes and smiling to me but then looking to the ground smiling?
Girls, Why whenever she walks passed me she keep looking to the ground smiling?
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