And yet there are humans that treat animals well (e.g. dogs, cats, crows and so on... ) These animals would feel the loss if humans disappeared. So i don't think it's right to say that nature (animals) wouldn't care and that the sentiment is a bit of implied put down of animals capacity for emotion and caring. Animals can care about their own and across species. Humanity would do well to feel less disjoint and separate from other humans and animals. That alone would reduce conflict a great amount and highlight the good that can be done between humans and animals.
As you probably noticed, I'm not fond of making a big distinction between humans and animals or nature. Hope that gives another perspective, and yeah, she probably was against the war and upset about the way humans were behaving at the time.