She was transported to a hospital, where she spent almost two weeks before beginning a 90-day rehab program in the beginning of August.
Sources close to Lovato told The Blast that she is "trying to live a healthy life and concentrate on remaining sober following her 90-day stint in rehab".
A source told the publication: "She just got back to LA a couple days ago".
According to People magazine, Twitter users claim to have seen Demi at Universal Studio's Halloween Horror Nights on Friday.
Lovato was in rehab for 90 days.
"I knew that she wasn't sober, but let me clarify: I didn't know what she was doing", De La Garza said.
She relapsed after leaving the facility and went into a sober living facility, allegedly her residence for over a year, TMZ reported in 2013.
"Yes, she has 90 days and I couldn't be more thankful or more proud of her because addiction being a disease, it's work", she said October 27.