What does it mean if a woman knows your name but you have never been introduced?

Anonymous
I see a girl at my gym who knows both my first and last name. Granted she works there but I have not been at that location for a few weeks and have not seen her there for longer. Yet she called me by my name and even used my last name when I asked if she knew what it was, without me checking in at all.
What does it mean if a woman knows your name but you have never been introduced?
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