Rhoda was the elder sister of Lavinia and Gwen's aunt. When Gwen stays with her while her Father is away in America, Rhoda takes it upon herself to try and make Gwen more of a lady rather than "one of those ghastly suffragettes!" needless to say they don't get along very well..
I can imagine! She's the kind of person you cringe about when you go out to lunch with them and they start complaining about things for the world to hear!