The point of contention is what amount of it is really her fault. You use the example of the cost of the bill... but really, what else -can- she say? It won't cost zero, but word from her superiors says it will. She cannot contradict that, but neither can she explain it because it's nonsense. Left with no other option to explain even to the most basic of questioning, she is really only left with one choice.
Obfuscate and distract.
This has been her option the entire time, and really her only one.
And the best way to do both is to... well, "[come] across as a big wanker like everyone else in DC right now", or more specifically the last option of a Press Secretary if no other ways to spin, elucidate, or control the narrative appear... is to be the biggest bitch/bastard in the room and focus fire on themselves.