The release comes a day after a judge granted her bail.
Mushtaq Awan says the girl left the prison in Rawalpindi, a garrison city near Islamabad, Saturday afternoon.
She has been held for a little over three weeks after neighbors accused her of violating the country's strict blasphemy law.
An Associated Press reporter on the scene says she was taken from the prison in an armored vehicle and whisked to a waiting helicopter while covered with a sheet to protect her identity.
Her lawyers say they will now push to have the case against her thrown out entirely.