Like Beast Boy, Beast Girl is the child of two scientists. And like Beast Boy, she was bitten by a green monkey and she was ill, until her parents used their skills to cure her with a serum that turned her green and gave her the ability to turn into animals.
Beast Girl looks and acts just like Beast Boy. The only differences are she has longer hair, visible eye lashes and wears a dress. Her hair is a lighter shade of green than Beast Boy's, and her dress is pink instead of magenta-violet.
Beast Girl is Beast Boy’s doppelgänger and female counterpart, together they are like brother and sister as they shared a similar origin story. Beast Girl (in a form of a giant snake) briefly ate the Titans and tried to eat Beast Boy as she thought she was the villainous Madame Rouge, but Beast Boy stopped her, saying she’s like a sister to him and so she spits the others out, however, when the real Madame Rouge is disguised as the Titans' couch and kidnaps the Titans, and Beast Girl and her team (the other Titans’ opposite genders) go to save the Teen Titans.
Beast Girl first meets the Teen Titans after she freaks out in a bathroom (like Beast Boy earlier in the episode) and ends up in the Titans Tower. The Teen Titans (except for Beast Boy) are not surprised by her appearance. When the Titans talk about Madame Rouge, she jokingly thinks she’s this so called Madame Rouge, and tries to eat them, but at the end she tries to save them along with a female Cyborg, male Starfire, female Robin (presumably the leader of the team) and a male Raven.
Beast Girl is one of the members of the Opposite Gender Titans. As all the Teen Titans occasionally think Beast Boy is a weirdo, it is presumed that the Opposite Gender Titans think Beast Girl is a weirdo. However, she commands her team quite well into saving the Teen Titans. However, when Beast Boy was chasing Beast Girl (after she thought he was Madame Rouge) both Raven and her male counterpart say “Weirdos” respectively referring to Beast Boy and Beast Girl.