(Fill in the blank) had a tremendous impact on Marie Colvin.

This may refer to two events in her life, one more personal and other related to her work.

In 2001 she lost an eye when covering the Sri Lankan Civil War. She was attacked by a rocket-propelled grenade while crossing from a Tamil Tigers-controlled area to a Government-controlled area; Then she walked more than 30 miles through the jungle and managed to survive and report the things that she witnessed while she was there. This event left post-traumatic stress disorder, and she required hospitalization following her injuries.

The other possible event is the death of her husband Patrick Bishop in 2002.

The first being related to her more known story is most likely the correct answer to the question.