Who is Jules from One True Thing and what is their importance?

Jules is Ellen's best friend in New York. Jules has wild black curls, a small pointed face, and a deep voice, three characteristics that exude false confidence. In truth, Jules is fragile - physically and psychologically - but no one really notices. Jules proves to be the only true support system Ellen has while she is caring for her dying mother, and Jules phones often to check up on Ellen, and Kate's, progress during the time they are living in Langhorne.