She doesn't step back. Dewey often gets into her personal space, she trained herself to ignore that, and even not to show disgust, only show that disgust later.

"Just for one or two games? Are you so easily bored?"

"Nirvash's threat are never idle. Nirvash means what Nirvash says, you'll see. When it's here someday."

But the thing is, Nirvash is NOT here. Not in Nexus, and won't be, but Anemone doesn't know that yet. If she knew, THEN she might be afraid.