Marla had apparently come to the conclusion that the U.S. military did indeed keep records of its civilian victims:

This time Ruzicka stayed in Baghdad longer than she had planned because she believed she had found the key to establishing that the U.S. military kept records of its civilian victims, despite its official statements otherwise, colleagues said.

This certainly sounds plausible; that they would count but not disclose. And it also sounds plausible that Marla could have found out about it, with her endless energy and ability to befriend everyone. I wonder if we will ever know what she had just been learning.