The Princess of Wales spent three days visiting landmine victims in Bosnia early last month on a tour organized by the US-based Landmine Survivors Network.
"This was one of the Diana's last efforts," Collins said. "I think that her tragic death will underline, highlight some of the things that she was most interested in, of course, keeping landmines in the forefront."
Millions of landmines remain scattered across Bosnia, following the three- and-a-half-year war that ended in late 1995. The mines maim and kill civilians almost every day.
Judy Collins has a long history of protest - singing and marching against segregation and theVietnam war, but was brought back into the political mainstream by President Clinton, who asked her to sing at his inauguration.
She has also suffered great personal sadness. Five years ago her only child, Clark Taylor, committed suicide at the age of 34.
She is widely known as the artist whose cover versions helped Joni Mitchell and Leonard Cohen to wider acceptance, and is best remembered in Britain for her hit versions of "Both Sides Now'', "Amazing Grace'' and "Send In The Clowns''.
Collins visited Bosnia for the first time in 1994, when, as a UNICEF representative, she volunteered to help promote the book I Dream of Peace.
Inspired by the writings and drawings of the children of former Yugoslavia, she wrote a song with the same title, which was included in her album Come Rejoice! A Judy Collins Christmas.
After her starring role at the President's inaugural concert, Ms Collins said: "It felt strange but very flattering to be inside the White House as a guest, rather than outside protesting.''