This was reported during my recent Breaking Dawn Update and now, GrandPa Carlisle confirmed it.
Well, the vampires are not getting any younger, not to mention Mackenzie's growth spurts. At age 10, she is growing as fast as Renesmee lol. I remember Panic Room's director, David Fincher mentioned that Kristen grew 3 inches during filming. She was smaller than Jodie Foster when the production started and towered over her when the final shots were done. A bit of trivia for you guys.