Joy first moved to Brazil when she was two years old. Her parents, the late Albert and Naomi Spieth, were BMM missionaries in Brazil's Amazon region. In 1967, Joy joined BMM and also served in the Amazon. In her more than 50 years in Brazil, Joy worked alongside Brazilian church planters and cared for financial needs on her field. Joy retired in 2020.
She wrote of her experiences: "It has been an incredible journey and God has blessed me all the way. I have met fascinating people, watch God perform healings, helped the lost find salvation, teach His word, teach music, witness miracles, and build churches. What an honor and privilege I have been granted by Him to further His Kingdom in the beautiful country of Brazil. Thank you, Lord, and thank you to all who supported me throughout my blessed life."