What does it mean when a girl is looking at a guy and smiles and narrows her eyes?

It's obvious when narrowing one's eyes means the person is annoyed. But what about when a girl is holding her gaze and smiles and narrows her eyes and opens them, with relaxed body language? Is that something along the same lines as a wink?
What does it mean when a girl is looking at a guy and smiles and narrows her eyes?
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