Amber Heard's Love for Newlywed Johnny Depp Has 'Changed His Life,' Friend Says

They married quietly earlier this week, but Johnny Depp and Amber Heard are preparing for a bigger wedding blowout in the Bahamas this weekend.

As the actors prepare to say “I do” – again! – in front of friends and family, those closest to them remember why Hollywood’s bad boy fell for his Rum Diary costar in the first place.

“She is a free thinker,” a longtime friend of Depp’s tells PEOPLE. “Her presence has changed his life.”

Depp, 51, and Heard, 28, got engaged in 2012 after heating up the screen as on-screen lovers in the Hunter S. Thompson adaptation a year earlier.

The key to their lasting romance, an entertainment source says, is that being with Heard is so different from Depp’s past relationships.

“Amber is a woman who can survive just fine without him,” the source tells PEOPLE. “She is not needy. He likes that.”

• Reporting by LINDA MARX