Who is Hixie Rice from The Cat Who Saw Red and what is their importance?

Hixie is a jolly girl who is rather chubby. Her greatest wish is to be married, something that is difficult because thus far..... she hasn't been able to find a boyfriend. Over the course of the novel, she admits to haveing had an affair with Dan, who refused to divorce his wife. His refusal leads her to end the relationship.