Mrs. Thomas was a wealthy mining heiress.
Mrs. Thomas' company leveled a 1000-year-old forest to build a strip mine, which earned her the ire of Poison Ivy. She was invited to the Eternal Youth Spa, but quickly found out she walked into a trap. She tried to flee in order to warn authorities, but Ivy caught up with her and turned her into a tree.
Her disappearance became a concern to her friends, who reported it to the Gotham police. Commissioner Gordon ordered a search of her residence, but could find nothing out of the ordinary. Batman later searched her home, and found a VHS tape advertising the Eternal Youth Spa identical to one he had received as Bruce Wayne.
According to Maggie Page, all of Poison Ivy's victim's were expected to recover.