The "Confident" singer was rushed to hospital in July after being found unresponsive from a suspected opioid overdose in her Hollywood Hills home, and has since checked into a rehabilitation facility to help her regain sobriety.
According to TMZ, Demi quietly transferred from a rehab centre on the East Coast to another facility world-renowned for its addiction programmes last month and has been visited by ex-boyfriend Wilmer on "several" occasions.
Eyewitnesses in a nearby town told the publication they have seen Demi and Wilmer at a local Starbucks numerous times, with staff at the coffee chain adding it appeared as though the couple were in a relationship.
Actor Wilmer, 38, was one of the first people to visit the "Sober" singer after her drug overdose and was spotted driving into Cedars-Sinai Medical Center in Los Angeles just one day after the incident.
The pair has remained close since parting ways in 2016 after six years together and appeared to break up on good terms, releasing a joint statement to Instagram celebrating their "loving and wonderful years together."
The duo has been openly supportive of one another ever since, with 26-year-old Demi revealing in her 2017 tell-all documentary "Simply Complicated" that she had "never loved anybody" like she loved Wilmer and will always adore him.
On Tuesday, the star's mother Dianna De La Garza confirmed her daughter was on the road to recovery and "doing well" following the incident, which apparently left her in a critical condition for two days.
"We just didn't know for two days if she was going to make it or not," Dianna explained in an interview with Newsmax TV. "I was very concerned, and I was trying to be strong for her and for her sisters and for my family back home. I just feel like the reason she's alive today is because of the millions of prayers that went up that day."