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BUENA PARK, CA - AUGUST 22: Demi Lovato and Wilmer Valderrama celebrate Demi's 23rd birthday at Knott's Berry Farm on August 22, 2015 in Buena Park, California. (Photo by Jerod Harris/Getty Images)

BUENA PARK, CA - AUGUST 22:  Demi Lovato and Wilmer Valderrama celebrate Demi's 23rd birthday at Knott's Berry Farm on August 22, 2015 in Buena Park, California.  (Photo by Jerod Harris/Getty Images)