Yes, I agree with Shara and Lord Darkhan. Timmain wanted to become an elf again. The Palace probably called to her elfin side, but she conciously changed herself. The thing with Winnowill and Rayek, Winnowill is making a choice for Rayek. He isn't unconciously changing himself. It's similar to her removing Windkin's blood, or shapechanging Tyldak. This time it's her spirit that does the work.