Who is Willa Mercy from Montana Sky and what is their importance?

Willa is the youngest daughter of Jack Mercy. She is a 24 year old young woman, raised on Mercy Ranch, Willa has spent her life trying to make her father proud of her. Willa's mother died when Willa was still a baby, making it impossible for Jack Mercy to send Willa away as he had with her two older sisters and their mothers. Willa was ignored for the most part by her father, and raised by the housekeeper, Bess Pringle.

Stubborn and spirited, Willa tries her best to make her father proud of her, working the ranch and striving to be everything Jack wanted in the son he never had. Despite this, Willa is left stunned when Jack's will leaves the ranch to the three sisters equally, provided they all spend a year on the ranch, working and living together. Willa is not happy with the arrangement and has no use for Tess and Lily, but her stubbornness does not allow her to give up.