Joe and Camilla first met on the set of the "Lovebug" music video in September 2008, and a month later he ended his relationship with Taylor Swift. A couple of days after breaking up with Taylor, in October 2008, Joe started dating Camilla.
Taylor wrote a revenge song about Joe titled "Forever & Always" as well as talked about their breakup on Ellen.
On the Jonas Brothers fourth album "Lines, Vines and Trying Times" Joe rebutted "Forever & Always" with "Much Better". The song is reportedly about Camilla and Taylor. The lyrics imply that by leaving Taylor, Joe found something much better with Camilla. However, Taylor decided to reply to Joe's song and wrote the song "Better Than Revenge" about Joe and Camilla, implying that Joe left her for Camilla. In this song, Taylor shades Camilla for being better known for "the things that she does on the mattress" and "stealing other peoples toys".
By July 26th 2009, Perez Hilton was reporting that they'd broken up and Joe cried a few times during the show that night and changed a line in Much Better to "now I'm done with movie stars".
Joe and Camilla were clearly not able to maintain a friendship immediately after breaking up, when asked in early 2010 if she was still friends with her ex, Camilla replied, "Um, no. Not really."
In a 2011 interview, Joe mentioned a girl from the entertainment world who broke his heart two years prior: "I won't say her name. But I was in a relationship, and we tried to work things out, and she, you know—I was really upset because she—she broke up with me."
Eventually, Camilla developed some kind of friendship with the Jonas boys. She came out to How to Succeed in April of 2012 to see Nick perform, and occasionally likes/comments on a few of Joe's instagrams. They even run into each other in September of 2012 at Runyon Canyon.
By 2013, Joe had clearly started viewing his past relationship with Camilla as more of a puppy love sort of thing, since he called Ashley Greene his "first serious relationship" in his Vulture article. Joe and Camilla caught up at a gala in October of 2013, and according to USWeekly, "For a solid 15 minutes before dinner started, Camilla and Joe had a one-on-one chat at his table. They ended their chat with a big hug."
In September of 2016, Camilla came to the LA show of Nick's tour (Joe's band DNCE also performed as special guests) and they apparently all had dinner together after Nick’s movie premiere a few days later.