updated 09/04/2012 AT 6:00 PM ET
•originally published 09/05/2012 AT 3:00 PM ET
“She’s already feeling better, stronger,” a friend of the country star tells PEOPLE in its new issue.
Rimes voluntarily entered an undisclosed facility the day after her 30th birthday “to learn and develop coping mechanisms,” her rep confirmed last week.
“I’m happy and healthy. I just want to be happier and healthier more consistently,” Rimes told PEOPLE before she checked into treatment. “I don’t want to wake up and not truly be enjoying my life and these amazing things around me.”