Lucy Westenra is the best-friend of Wilhelmina Murray. When Mina's (Wilhelmina) fiancee, Jonathan Harker, was away, Lucy invited Mina to stay with her. It was then that Mina realized Lucy was a sleepwalker. During one such occasion where Lucy was sleepwalking, Dracula encountered and bit her.
Lucy's health begins to deteriorate due to his continued visits to feed on her blood. After two bites, Dr. Seward seeks the aid of his mentor, Professor Van Helsing, as he doesn't know what's causing her illness. Helsing instantly identifies it as a vampire attack but brushes it off as a normal sickness and suggests using garlic as a remedy when really it'll ward off Dracula and keep Lucy safe. It nearly works but thanks to Lucy's mother who unwittingly removes the garlic, Dracula breaks in and finishes his deed.
Lucy dies from the final feeding, allowing the vampirism to transform her body into the walking undead. She begins to start spreading her own vampire bites around to little children, who dub her "The Bloofer Lady" (child speak for "Beautiful Lady"). Mimicking Dracula's attack on her with the intent of draining children gradually until they eventually weakened, died and turned into vampires themselves who would go on to spread it to others. Helsing realized this and gather the other protagonists (Seward, Quincy and Arthur, all three suitors to Lucy) to stop her.
The confronted her near her tomb where she was buried and waited till she returned. Helsing forced her back into her coffin before having Arthur (her fiancee) stake her, killing her for good.