Williams first trained as a teacher of English as a Second Language (ESL), receiving a BA from the University of Vermont in 1972 and a Master's degree in teaching Spanish and ESL from the School for International Training (also in Vermont). She taught ESL in Mexico, the United Kingdom, and finally Washington, D.C. before her first appointment in aid work, becoming a coordinator of the "Nicarague-Honduras Education Project" form 1984 to 1986. She then became deputy director of a Los Angeles-based charity, "Medical Aid for El Salvador", a position which she held until 1992 when she took up her position with the newly formed ICBL.
The organisation ultimately achieved its goal in 1997 when an international treaty banning antipersonnel landmines was signed in Oslo in 1997 (though not all countries have signed the treaty, notably the United States).
She continues to serve the ICBL as a campaign ambassador and editor of the organization's landmine report, and is a visiting professor of social work at the University of Houston for the 2003-2004 academic year.
She has written and spoken extensively about issues relating to landmines.