She was played by Natalie Denise Sperl.
Lilith first encounters main protagonist Adam at one of his beach parties, and makes an impression on him during a sexual encounter; even leaving marks on his chest. She resurfaced at another one of Adam's parties and catches him with two women, who she orders to leave before forcing herself on Adam once again. After this, Lilith continues plaguing Adam, doing so by drowning his girlfriend, Heather, in their swimming pool. She later invades a flight session and nearly causes one pilot to crash with her wild moves. Later on, Lilith follows Adam and his best friend, Jason, to a nightclub, where she takes Jason and later snaps his neck, killing him. Adam frets over the loss of his best friend and girlfriend as he watched a video of the three of them together, but at that moment, the evil Lilith taunts him by popping up on his computer.
Lilith engages in a final encounter with Adam at his home, and she continues to taunt him over his objects that he acquired to deal with her. She morphs into her demonic form and lunges after Adam, but at that moment, he holds at bay before killing her with a sword through her heart. Police are actually called to Adam's house and he's arrested for murder, especially after he gives the true details of what happened. As for Lilith, she was in the back of a coroner's van being groped by a male coroner, only to revive and brandish her demonic red eyes. Lilith laughs evilly as she kills her latest victim at the end of the movie.