Josephine Iyamu made her victims swear oaths to hand over money during "juju" ceremonies which saw them ordered to eat chicken hearts, drink blood containing worms, and endure powder being rubbed into cuts.
Jurors were told the 51-year-old then arranged for the women to be trafficked across the Mediterranean - with one being told to pay a "bill" of 37,000 euros.
Iyamu, formerly of Wilson Grove, Bermondsey, south London, was convicted on Thursday of five counts of arranging or facilitating travel for sexual exploitation after a ten-week trial at Birmingham Crown Court.
Jurors also convicted the Liberia-born British citizen of perverting the course of justice by arranging for relatives of the complainants in Nigeria to be arrested.
Her husband, 60-year-old Efe Ali-Imaghodor, was acquitted of doing acts intending to pervert the course of justice.
Iyamu is believed to be the first person to be convicted under Modern Slavery Act laws passed in 2015, allowing prosecutions of British citizens for sexual trafficking taking place overseas.
The National Crime Agency (NCA) said Iyamu forced victims to take oaths that bound their loyalty to her on pain of death.
Iyamu, who was made a British citizen in 2009 having been allowed to stay in the UK due to her nursing qualifications, is known to have declared a modest income of around £14,500 in 2016/17 from her work as an NHS agency nurse.
But inquiries after Iyamu's arrest in 2017 found she was able to afford to spend thousands on international air travel and to afford a large home in Benin City in Nigeria - complete with servants' quarters.
Prosecutors said the voodoo rituals gave Iyamu crushing psychological control over the women, who were too afraid to challenge her or to fail to pay her back tens of thousands of euros she charged them to be trafficked into Germany.
Opening the case at the start of the trial, prosecutor Simon Davis told jurors: "Josephine Iyamu had a network of people who assisted her with trafficking the women from Nigeria overland to Libya - across the Mediterranean Sea to Italy and from Italy up and into Germany.
"She was there on the mobile phone along the way but her real role was at the end of their journey - when it came to getting money from the women and making a profit out of their exploitation.
"The debts incurred by the women were enforced through fear. Each of the women were put through what is known to some as a voodoo ceremony.
"Iyamu and others involved with her were willing to put these women at risk of serious injury and or death as they made their journey from Nigeria to Europe."
Sentencing will take place next Wednesday.