Hilda and Sabrina are turned into stone and then crumble. The statues are a very light grey and have an almost marble-like appearance. They appear to have no pupils or irises. Hilda crumbles and is put back together by a sculptor after a failed attempt to just piece her back together.
From Wikipedia - "Hilda is on the rebound after she breaks up with her boyfriend, so she meets a guy named Will. They instantly fall in love and want to get married. Though Sabrina and Zelda think this love should not be, they plan to break up the couple. As soon as Zelda throws herself at Will, Hilda breaks up with him but then she turns to stone and falls to pieces. Once knowing Hilda's love was true, Sabrina takes Stone Hilda to a place where she can come back to life. Sabrina must gamble her true love to save her aunt's life. Sabrina then turns to stone and falls to pieces."