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Linda is Willy's doting wife. She refuses to see through her husband's lies. This is a woman on a mission: protect Willy's emotions and dreams. Part of her nature is the result of naïveté; Linda doesn't know the full picture here, from Willy's finances to his job to his mistress. This cluelessness is partly why Linda defends her husband's behavior even when he has lashed out at her. No one can argue—she's one loyal chick.
Like her husband, Linda equates happiness and freedom with material wealth. She accepts the American ideal that success is possible for anyone. Nevertheless, Linda shows substantially more preoccupation than her husband with talent, dedication, and basic ethics that reach beyond simply being well-liked. Unlike Willy, she expresses concern over Biff's poor math performance, his growing aggression, and his tendency to steal everything that will fit in his pocket and even some things that don't.
Linda's utter and blind devotion to her husband makes it hard for her to understand why he killed himself—and why no one showed up to his funeral. Her ironic statement "we're free" just reminds us that Linda is still very, very clueless.