Lovato is "not thrilled" about Valderrama rekindling a romance with Kelly, 36, according to the insider.
"It is kind of questionable that he would be with someone he's already dated," the insider tells Us.
This is somebody I really care about,'" she told Cosmopolitan last year.
The stars are the latest victims of an already vicious summer of Hollywood breakups.
The two made it Instagram official after he posted a photo of the two on a walk and captioned it with a heart emoji.
Vasconcelos posted another photo with Lovato on New Years, which leads us to believe these two are more than just casually dating.
The "Confident" singer began dating Valderrama — 12 years her senior — shortly after she turned 18.
Soon after, she checked into rehab for three months for bulimia, a self-harming disorder and drug abuse.
Vasconcelos loves to repost her workout sessions on Instagram and even posted a video of her supporting him during a big fight over the summer of 2016.Demi Lovato just stepped out in NYC with her new boyfriend, UFC fighter Luke Rockhold.The couple was spotted holding hands while walking into Madison Square Garden for UFC 205, seemingly confirming their relationship.The duo expressed they struggled with the "difficult decision" but ultimately discovered they work that "more than anything we are better as best friends." Demi Lovato talks boyfriend Wilmer's loyalty Valderrama, 36, and Lovato, 23, dated on and off during the beginning of their tumultuous relationship, but had been going strong for the past two years.The longtime friends promised to "always be supportive of one another." The former Disney star has frequently praised the "That '70s Show" actor for helping her battle her drug addiction.