Her name is Jodelle Ferland. She is 14. She is the newest addition to the cast of Eclipse, playing newborn vamp Bree, who gets a little crazy if you all remember correctly.
Personally, I was under the impression Bree was a bit older. BUT, maybe theyre trying to pull off another Kirsten Dunst in Interview With A Vampire.
Like I always say, I am so down with murderous little children.
You can also follow her on Twitter if you feel so inclined: http://twitter.com/jodellemicah