I am confused why she said that?

I have been pursuing a girl and she clearly knows I like her. Recently when I talked with her friend and reached the topic about her, her friend joked about how she said I am more compatible with other girl (I’m not completely interested) whom I am close with at office. I’m confused why she said that. It is because she is not interested in me or testing my reaction? Or is it just a joke?
I am confused why she said that?
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