The Identity of "A" Was Finally Revealed in the "PLL: Original Sin" Season Finale

We find out in episode six that Rose had a mental breakdown after Angela's death and was committed to the Radley Sanitarium. However, when the sanitarium was converted into a hotel, Rose was released. It seemed like there was a chance she took her time to grieve and then returned to make the sinners pay for their role in her daughter's death. But we find out in episode eight that Rose died and her body is being kept inside of her house by Clanton, Aaron, and "Crazy Joe."