Again, Eve is playing the villain. She is scaring Tarou into action, going full scorched earth so that he can freaking choose the true person he loves.
Eve is ready to dissappear, she has been trying to understand the process of dissappearing by going "into" something. Just like the zombie that went into the painting. The one you could say it was a similar existence to her. If, and only if, Tarou chooses ibusuki then the most likely scenario is that Eve goes into Ibusuki, not possessing her but maybe freeing her of the ability to see zombies (how? ending magic of course) heck the author can add a different colored strand of hair growing on ibusuki's head showing that Eve and Ibusuki have become one and the same. (If we go for some lols then Eve also gives her some extra chest sizes xD).