Sandy Springs police say 23-year-old Qianying Zhao of nearby Doraville was found at the home shortly after 5 p.m. Wednesday. The home is owned by music producer Dallas Austin.
Police say she told officers that she had come to attend Bieber's birthday party and entered the unoccupied home through an unlocked door.
But police say Bieber's party was earlier in the week at another location.
Police say she told officers she was Bieber's friend, but investigators believe she's one of millions of fans who follow him on Twitter.
She faces a charge of criminal trespass. It wasn't immediately known whether she has an attorney.