Who is Teresa from Friend of My Youth: Stories and what is their importance?

Teresa is the war-bride of Reuel, who traveled to Canada from Europe with him. She owns a store on the highway outside town, where Margot and Anita used to stop for coffee on their way to school. Teresa is the woman who is damaged by Margot and Reuel's relationship. She is left alone, cast aside and forgotten. Reuel is all she had, and she had tried to hold desperately onto him even when it had been clear that their relationship was failing, long before he had become involved with Margot. Teresa puts all her energy into loving Reuel and is left with nothing when he leave her. Unlike other characters in this collection, she does not recover and learn to pursue her own goals, but falls into hysteria and is driven mad. Now she can no longer distinguish fantasy from reality.