Allie X's signature cropped from the postcard which comes with The Story of X Chapter 1. It is not handwritten, but printed. (vectorized on Inkscape)
The Story of X: Chapter 1 https://web.archive.org/web/20150602182917/http://phi.boutique/the-story-of-x%3A-chapter-i-allie-x-01/dp/732
Allie X