It drives her crazy that her son died for a cause he believed was worth dying for. She can't bring herself to hate him for it, so she turns her rage on President Bush and anyone else who supports the effort her son willingly died for.
A common problem among liberals:
'Narnia represents everything that is most hateful about religion' (The Guardian, UK)
"Of all the elements of Christianity, the most repugnant is the notion of the Christ who took our sins upon himself and sacrificed his body in agony to save our souls. Did we ask him to?"