Although Mackenzie Foy is playing Renesmee Cullen in Breaking Dawn, they still needed another girl with Mackenzie’s body structure for the stand-in and photo-double. According to IMDb, Haley Duryea is the lucky girl who gets to take on the stand-in job!
Keep in mind that she is not required to look like Mackenzie, she only needs to have a similar body structure. I am going to assume she’s being used for ‘older Renesmee Cullen’ stills since Hayley is clearly taller/older. They will simply add Mackenzie’s face to Hayley’s body. 
Poor Bill Condon. The joy it must be trying to create a child who grows at an extremely accelerated rate. You can see more pics of Hayley here.
