Theresa is the youngest of 12 siblings, from a family of traditional rulers in the Dedza District around Lake Malawi, she was descended from the Chidyaonga line of the Maseko or Gomani dynasty. She worked as a secretary for nearly 30 years at a college, in the Zomba district of southern Malawi. She married & became the mother of 5 boys. In 2003, the chiefs of the Dedza District chose her as the next head chief of the area, where almost 1 million people lived. She said she was chosen because "she was good with people". Theresa accepted her position, then moved to Lusumbwe, which is one of the main ports on Lake Malawi. Upon her arrival she donned the traditional red robes, beads & leopard-skin headband. As head chief she was given the title, Inkosi Kachindamoto VII.

Malawi is one of the poorest countries in the world & has an HIV infection rate of 10%. A UN survey in 2012, uncovered the fact that more than half of the girls in Malawi were married before the age of 18 & ranked Malawi as one of the countries with the highest rates of child marriages, which increased in rural areas. Young girls sometimes as young as 7, are subjected to sexually abusive traditions that include, sexual initiation camps for "cleansing". In 2015, Malawi passed a law that forbade marriage before the age of 18, but law enforced by tribal leaders still said that children can marry, as long as they have their parents consent.

Theresa was disturbed to see the high rates of child marriage in Dedza. Though she couldn't convince parents to change their views, she had 50 lower-ranking chiefs in Dedza agree to abolish early child marriage & annul existing customs. She stripped 4 other chiefs of their power, as they were responsible for the continuation of child marriage in their districts; but later reinstalled them, after they had annulled the marriages.

As of 2019, Theresa has had over 3500 child marriages annulled, bringing her to the attention of the international community. The marriages that were annulled were sanctioned by tradition, monitored by chiefs, rather than civil marriages. Chief Kachindamoto worked with mothers, teachers, village committees, religious groups & non-government organizations. Not unexpectedly, she met plenty of resistance from parents & couples themselves, particularly impoverished parents when the dowry had been paid. But she felt the success of her annulment campaign came from going door-to-door to talk with her people.

In June 2015, she told a newspaper, "I have terminated 330 marriages, 175 which were girl-wives & 155 were boy-husbands". She went on to say, "I don't want youthful marriages, they must go to school. We now have set our own laws to govern everybody within my area when it comes to child marriages... no child should be found loitering at home... during school time".