I'm confused if in breaking dawn it ends with renesmee about 5 so why are they casting teenage renesmee.??? What am i missing???

When Nessie is at the actual age of 5, she'll look much older than that! Mackenzie Foy (the actress that will play Nessie) is only 9. There have been rumors going on for a while that Christie Burke will play an older version, but that hasn't been confirmed and I highly doubt it's true. They will use CGI to morph Mackenzie's face onto the body of a younger child.

Best there are going to show her all grown up and her perfect life with jacob :)

I am pretty sure that Renessmee will get to at least ten years old but I am not positive. I am confused too so do not be embarrassed! I am asking the same questions!

she is a vampire and vampires grow qickly