In 1825, Opie joined the Society of Friends, due to the influence of Joseph John Gurney and his sisters, who were long-time friends and neighbours in Norwich, and despite the objections made by her recently deceased father. The rest of her life was spent mostly in travel and working with charities. In the meantime, however, she published an anti-slavery poem titled, "The Black Man's Lament" in 1826 and a volume of devotional poems, "Lays for the Dead" in 1834. Opie worked with Anna Gurney to create a Ladies Anti-Slavery Society in Norwich. This anti-slavery society organised a petition of 187,000 names that was presented to parliament. The first two names on the petition were Amelia Opie and Priscilla Buxton. Opie went to the World Anti-Slavery Convention in London in 1840 where she was one of the few women included in the commemorative painting.