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It's really early for me right now, having been up since 4am, but I can't seem to find the tab for the flirting.
While I don't do the flirting on my main doll, I do have a couple who I try to flirt with.
Am I just not seeing it because I'm half asleep?
Click on the red hearts button under your loft.
It'll show every man you ever flirted with and there'll be a big button if you scroll down. Click it :)
You could also flirt by clicking the level button. Scroll down and you'll see the flirt button.