Who is Rhian Evans from A String in the Harp and what is their importance?

Rhian Evans is Becky's best friend. She lives on a large farm with her family, speaks with a Welsh accent, and is described as small and dark, with long braided hair. Contrary to her appearance, Rhian is loud, brash, and talkative. Over time, she proves herself to be a good friend to the Morgan children.