Girls, what does it mean when she smiles and looks away quickly?

Ok, i'm 14 and I have a crush on this certain girl. When ever I look at her she smiles at me and looks away. On a occasion or two she will talk to a friend they will both look at me and look away quickly what does this mean? And sometimes she looks at me and I can see it in the corner of my eye. I've tried messaging her but she responds with one word answers. Does this mean she's shy or just isn't interested, Or does she know I like her? Any feedback would be great.
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Thank you everyone !
Girls, what does it mean when she smiles and looks away quickly?
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