Who is Penelope Rodger from For the Sake of Elena and what is their importance?

Penelope, better known as Pen, is Lady Helen Clyde's sister. Before marriage, Pen was employed at the Fitzwilliam Museum, where she worked in art restoration. After marriage, her husband Harry Rodger convinced her to stay home and raise their family. Pen resents her husband's outside the home and the loss of her own.