Lily was an employee of the Eternal Youth Spa.
Violet and Lily served under Poison Ivy during her operation of the Eternal Youth Spa. To the outside world, the girls appeared to be hosts, but in reality, they helped Ivy with her plan to punish those guilty of environmental degradation by turning them into trees.
Although a capable henchwoman, Lily does not do much thinking for herself, and shows an apparent lack of education, hence the typical "dumb blonde". When Batman confronted Poison Ivy alone by saying he deduced her alias of "Dr. Daphne Demeter" based on Greek mythology, Lily suddenly appears and says of course, as Poison Ivy has a high school diploma, something she apparently lacks.
Though they were handy help against industrialists, Batman proved a tougher opponent. Violet was first to be bound, and Lily shortly after.