Doubts are natural, even in saints
Not the first example I've read about. Some of C.S. Lewis' best writing was about those times his faith failed him.
Unless one had been lobotomized, it would be impossible to work where she worked and not have doubts about the compassion of God. And yet, she still did the good works.
Somewhere I remember a Bible verse (I don't know which one) that, paraphrased, says something along the lines of "Blessed are those who do not believe in me, yet still do my will."