"We were in a relationship and we broke up, and at one point, I was really mad at him," Lovato said.
Indeed, not too long after their May 2010 breakup (which happened directly before the two former Disney stars were about to hit the road on their Camp Rock 2: The Final Jam tour), Jonas, 23, was seen getting close to Twilight actress Ashley Greene, whom he dated until March 2011.
Now, three years later, the X Factor judge, 20, says she and Jonas have been able to get past their failed romance and maintain a friendship, although it can be difficult at times.
"When you go through heartbreaks and things like that, you always have in mind somebody," she said. "It's like when you hear a song on the radio that reminds you of somebody, you're going to be reminded. But keeping that in mind…it's a delicate balance."
She continued, "Now, I can, fortunately, say, that him and his brother Nick, have always been there for me, and are literally family, and like brothers. We have a great friendship. And we may not be as close as we used to be, but that's OK."
Jonas, who said it was his "choice" to break things off with Lovato in 2010, is trying to be a good friend and support system to the "Heart Attack" singer.
On Tuesday, May 14, he tweeted to her, congratulating the star on her new record, Demi, that hit the same day. "So happy for you!" he wrote.
As Lovato -- who was treated for personal and emotional issues at a rehab facility in 2010 -- puts it, her heartache over Jonas was just another thing she had to learn how to overcome in her life.
Debuting a brand new tattoo this week on her shoulder, one that reads "now I'm a warrior," (in honor of a new song titled "Warrior" on her new album), the former Sonny With a Chance actress says that she's feeling stronger than ever these days, and she hopes her music reflects that.
"It's a very powerful song," Lovato said of "Warrior." "It is the song that I want my fans to hear, and apply it to any situation that they can relate to."