Objectively everyone knows Japan has no independent say in this, if US chickens out they'll be ordered to sit down so to not drag US in through their defence treaty, and if US want to fight Japan will be ordered to jump in first because they're an expendable tool.
So it was never about the content of what she said but rather the fact that she said anything. There's nothing Japan can spin nor explain nor justify because the content doesn't matter, no more than an animal can explain why they did an animal thing to a human. For all practical purposes China has simply decided to punish Japan for barking, the only question is if China's long term goal is to train the animal, or to cull it.