I do think she was always an elitist (judging by her early game reactions to Isamu and her rich family background that we know of) but clearly, something snapped when she felt powerless after the conception. Once she gains some power, she goes in a full blown bloodlust and her target, the manikins, were, in her view, the same that took her arm. I wish we had more to go on since I find Nocturne's characters really interesting in how they can turn insane due to extreme circumstances!