"She is staying at her mom and dad's house, where Jessica has been staying," a source close to the singer tells PEOPLE. "She is getting better. She is looking forward to vacation."
Simpson, 21, collapsed in Tokyo on Thursday following a performance on MTV Japan and was taken to an area hospital by ambulance. She was forced to cancel her appearance at Monday night's Radio Music Awards in Las Vegas.
For the past two months, Simpson has been doing appearances in support of new album I Am Me, which debuted atop the album charts in October.