Is a girl exposing her belly button (in a business setting) making a flirtatious gesture?

Late in the day when everyone else had left, my coworker came by my desk to chat. While we were talking, she started fixing her hair and her shirt rose up so I could see her bellybutton. And while I did well to focus on her face, I'm sure she knew her belly was exposed. Obviously, on the beach this wouldn't make we wonder. But this felt flirtatious. Am I wrong?
Is a girl exposing her belly button (in a business setting) making a flirtatious gesture?
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