Lilly Thayer is one of the pre-made downtownies in The Sims 2: Nightlife. She can be made playable by befriending and asking her to move in, or by marrying her. Lilly's career is randomized at the start of the game, and she is mainly interested in Food, Paranormal, Travel, Sports, and Work.
Her name is randomized when Downtown is generated. The name "Lilly Thayer" is only referenced in the game files. Like most downtownies in The Sims 2, Lilly has a customized facial structure. She uses a customized version of the 23rd Maxis face template in Create a Sim, except the eyebrows use the 5th face template, and the jaw uses a different face template.