Laura

Laura is an anime-only baobhan sith who infiltrated the Hellsing Organization and tried to turn Integra Hellsing into a ghoul. Apparently possessing great hypnotic powers, she got in without suspicion by mentally convincing everyone (except Alucard and Seras Victoria) that she was Integra's nonexistant sister. In what is widely considered the most risqué scene in the series, she paralyzes, partially undresses, and bites Integra on her breast. Integra realizes then that she has no sister, and that the girl must have tricked her. Laura then stabs Integra in the stomach with a knife to begin drinking her blood, but is soon dispatched by Alucard, who'd been delayed in an encounter with Incognito.

The text of the English dub is somewhat confusing, probably due to nonrecognition of the term "baobhan sith" (especially when rendered by a Japanese speaker). The original script is clearer: Laura took her name from the novel Carmilla (which, like Dracula, may be close to the truth in the history of the Hellsing world), but Integra also addresses her as a baobhan sith. Upon realizing her identity, Integra refers to the baobhan sith as the Countess Karnstein, this being another reference to the classic vampire novel Carmilla.

A baobhan sith is a Scottish folk creature, a female vampire in a green dress and with very pale skin. It is pronounced "baa-van-shee." In the Japanese version of the anime, this got rendered as "Buubanshii", which is part of the source for the confusion on her name.