When she doesn't know what she wants, though? She flounders hard and shuts down.
*nods* Well she does know what she wants: She wants her baby back. But everything is hopelessly convoluted, and her baby is all grown up and happy with how her life turned out... (And we're back in Persephone territory, with River practically stealing herself out of Amy' arms.) All that's left to her is revenge (and that she gets!).