A Magpie
A magpie is a famous person who swoops in like a thief and snatches the person you were chatting up. They're usually full of hot air and drama.
My crush was talking to my friend, and then a magpie swooped in and took him to a fancy restaurant.
I was talking to the cutest guy at the café, but then a magpie came in and stole him like he was a piece of cake.
My best friend was chatting up my crush, but then a magpie showed up and took him to a concert.