The Legend of Molly Briars of Beelsby; Molly Briars’ stone.

According to old folklore, at midnight on the 21st of June each year, the ghost of a maiden, called Molly Briars, is seen sitting on the stone milking a white cow. If the stone is moved, it will bring bad luck and, for example, all the local cows will die. ‘A History of Beelsby’ by A. C. Sinclair (1947) refers to the ghost and says that it haunts the valley through Barff Bottoms, Beelsby. The tale certainly pre-dates the 1940s. In the 1960s/1970s, the stone sat higher on the ground. The 50p piece placed on the stone is for scale. Can anyone add further information to this legend?