Other mistake: Sara is typing a message to her boyfriend. It shows up as "u ignoring me?" but you can see that she's typing something else on the keyboard. (00:38:45)
Continuity mistake: While mother and daughter are at the park, when the mother looks at the girl a train is passing on the tracks next to the park, but when the camera switches to the mother there is no train, then when it switches back to the girl the train is there again.
Answer: It's a derogatory slang term made up for the show.