The singer was in rehab since being hospitalised for a nearly fatal drug overdose in July.
"Demi looked great and so happy to be out. They seemed like good friends who were catching up and excited to see one another. There wasn't any PDA or romantic gestures, but she was smiling and laughing throughout dinner.
"She was very relaxed and at ease. She said hello to the sushi chefs when they greeted her with a big smile. She seemed happy and healthy. They stayed for an hour and a half before leaving together in his car," an eyewitness told E! News.
Several people tweeted that they spotted the 26-year-old singer at Universal Studios' Halloween Horror Nights on Friday.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)