Joyce becoming an atheist is actually really tragic. Unlike Becky, she wasn't a repressed teen who discovered a world outside of her hometown that she liked better; Joyce genuinely liked all the bland evangelical crap she was raised on, loved her faith and had a great relationship with God. If her parents sent her to a Bible college like Becky she'd be perfectly happy. But she went to IU, made friends with lesbians and atheists, and to protect those friends decided she had to abandon everything she used to enjoy, including her religion. There's no empowerment or freedom, Joyce is still desperate for authority figures and is as terrified of being a bad person as she was before. She never internalized "I can say and do what I want and don't care who hates me for it" like Becky has.