Who is Melanie from Oranges Are Not the Only Fruit and what is their importance?

Melanie is Jean's friend and later becomes her lover. Jean first noticed Melanie while she was working in a market and proceeded to go there every Saturday just to watch her. When Melanie leaves her job at the market, Jean searches for her, and when they finally meet, Jean invites her for a baked potato and Melanie agrees. The two go onto become lovers, something that apparently disturbs Jean, who tries to tell her mother but can't admit to the details. Her mother, intuitively, discerns the nature of their relationship and turns it over to the church. The girls are confronted and Melanie succumbs to pressure, repenting of the lifestyle. She goes onto marry a man, who knows about her relationship with Jean, and has a family. Jean is bitter.