Episode 288 introduced a character named Ran. It doesnt take a rocket scientist to figure out that connection.
Not only does she look just like Rin(sans the cheek markings) but in a transition from a flashback about Kakashi,Guy and Rin she took Rins place.
Another thing that caught my attention was when Ran said" so you got your revenge".
This could mean that either she was related to Rin and knew that the Mist was the reason for her death or the animators made a mistake trying to foreshadow events.
Too many coincidences or naa.