1. She is overly flirty with your fella. Adding him as a friend on Facebook, fine. Sneaky live chats behind your back, not fine.
2. She bought the dress you have been eyeing up for months, swearing blind that she never knew you wanted it.
3. She begs you to be her date to a wedding, only to ditch you at the first sign of the hot best man.
4. She gets off on your bad news. It's a radio silence when you get a promotion, but break down in tears and she's pouring out advice.
5. An office frenemy will suck up to the senior staffers, while being ever-so-slightly patronising toward you.