Who is Anne Gascoigne from Daniel Deronda and what is their importance?

Anne Gascoigne is Gwendolyn's cousin and Rex's sister. She is initially quite taken with Gwendolyn, though she becomes angry with Gwendolyn for her treatment of Rex. Anne is described as a quiet, unassuming, young woman, who believes that she will never marry but will remain her brother's housekeeper all her life.