In the end, she ordered the masked killer to stab Dylan, but the hero managed to turn his arm, and he accidentally stabbed Aileen instead. Knowing about her impending death, she cursed her accomplice of being an idiot, and told him, that she most likely would have killed him anyway, to cover the tracks of her crimes.
Note: At one point, long before her villainous reveal, it seemed, that the masked killer slit Aileen's throat, therefore tags "Graphic Demise" and "Back from the Dead" had been applied. At the same time, Dylan Dog seemed to have sex with Aileen under the shower, but this was some kind of phantasm. (Therefore the tag "sex" was not used, because it was not actually her, although there is little doubt, that Dylan and Aileen had been together before.) In this part, the story is vague and supernatural. It appeared, that "the destiny" was playing a trick on Aileen, because she was pitching her serial killer as "destiny". Aileen seemed to think the like herself during her long, but less excessively bloody actual death scene, and later dismissed the thought.