You're overthinking that a bit, BMM. If Gilman "applied evolutionary theory in the movement for social change" and was identified as a "social theorist," it's no leap to call her and those with whom she identified "evolutionary theorists." Also, look at this language in the first paragraph:
Another, more activist group of Social Darwinists held that although changes in human societies, like those that occur in biological species, do constitute a sort of evolution...
This is the group that Gilman identified with. Again, it's no leap to call these Social Darwinists evolutionary theorists, since they have some theories about evolution within societies.
Don't look for ways to pick an answer apart, because when you take that approach you can too often find some minor detail to quibble over. Instead, remember the instructions to select the best answer, as opposed to the "correct" answer or the "right" answer. If the answer is better than the other 4, then no matter what minor complaints we have about it (and I have had many minor complaints about a lot of correct answers over the years!), it's still the best answer and therefore the credited response. Pick it, even if you don't love it, and move along to victory!
Adam M. Tyson
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