a person who leaches the friendship right out of someone and when it comes turn to return the favour, they walk away and leave them with nothing. i.e. receives gifts, money, food, help from a friend then turns around and gives none in return.
friend one: "what ever happened to that friend of yours?"
friend two: "oh, it turned out she was a possingham"
friend one: "what do you mean?"
friend two: "she never helped me when i needed the help most"