Complex sentence: According to her, she herself used to be a sorceress until due to the world's Balance collapsing and believing people stopped believing in magic, she lost her magic and reduced herself to sell cloaks.
Split into simpler sentences: According to her, she herself used to be a sorceress. However, due to the world's Balance collapsing and the people's failing belief in magic, she lost her magic and reduced herself to sell cloaks.