User blog comment:Derax-Pagani/Chapter 502 Review/@comment-24784846-20160917221849/@comment-7418318-20160918101841

But why would she even bother to make the illusion of Zeref if she was already away.

It was in Mavis' best interest to keep Irene thinking that she was still there on the table and creating an illusion of Zeref had a good chance of giving the truth away (which it did).

Mavis wouldn't reduce her chances to get away just to taunt Irene in an attempt at petty revenge.