Ruby Ann Hatfield is a downloadable Sim first seen on the official The Sims website. She is wife to Ulysses and mother to Billy, Hank, and Elizabeth. Her relationship panel shows that she and her husband are friends, but are not in love with one another. She works in the Medicine career as a Medical Technician, and has no skills. Her bio implies that she is pregnant with her fourth child; however, since pregnancy did not exist as a game mechanic in The Sims, it is up to the player whether to expand her family or not.
It is possible that she has some connection to Ruby Broke in The Sims 3, since they are of similar appearance (allowing for the 25 years that theoretically passed between the two games), temperament, and economic status; but this is purely speculation.