"Esa chica, ¿la conoces?"
Translation:That girl, do you know her?
Depends on prior context. If the conversation starts with "Do you know that girl?" as you point at her, fine. But lets say you are talking to another student and you say. "Some girl just shot the professor!" The other student says, "Which girl?" to which you reply, "That girl, do you know her"?, as you point to the girl with long black hair, black eye shadow, and a smoking gun.