Yep, absolutely true that she was Liza in a recording or a workshop, or some early stage of the show.
She said later she didn’t particularly like the material for The Witches of Eastwick. In fairness, she was given some of the weakest material for the demo. I think she only sang ‘Eye of the Beholder’ which has always been a bit of an unfulfilling mess. I’m not sure who sang the role of Alexandra in the other bits. Some was the composer himself.