Greene was born in Jacksonville, Florida, and is the daughter of Michele (née Tatum), who works in insurance, and Joe Greene, a U.S. Marine who now owns his own concrete business. She grew up in Middleburg and Jacksonville, and went to University Christian School before transferring to Wolfson High School when she was in tenth grade. She moved to Los Angeles, California, at the age of 17 to pursue an acting career. Greene has an older brother named Joe, who still resides in Jacksonville with their parents.
Greene is good friends with her Twilight co-stars, particularly Kellan Lutz and Jackson Rathbone whom she knew before filming of the series began. She dated singer Joe Jonas. The two broke up in March 2011. Greene has stated the she grew up watching football and is a Florida Gators fan. She was also seen attending a Green Bay Packers game against the New York Giants with Jonas and Jessica Szohr at Lambeau Field in 2010. In 2009, nude self portraits of Greene were leaked onto the internet. Her attorneys threatened to sue various websites that published the pictures.
