Elliot's book, Through Gates of Splendor, relates this remarkable story, about which the following gripping film was also made:
Even more remarkably, in a daring adventure of breath-taking commitment, Elliot (accompanied only by her daughter), returned to continue a ministry of Christian forgiveness and share the Gospel with those who had killed her husband and those of several other widowed women who returned to the United States. The result was the conversions of many to Christ and a remarkable transformation of the tribe from one engaged in continual blood letting to a peaceable people changed by the power of forgiveness.
The magazine, Christianity Today (June 15, 2015), has a substantial article on Elliot HERE.
[Hat tip to JM]