I have a few questions with this. How did she give birth? Tbh I made an Oc back when Jacob came in which was Mavis and Zeref's daughter (Unrelated I know) Maybe the last scene which Mavis and Zeref were together, maybe It was the time when they had "it" Which resulted in her dying. But if what she said is true when they kissed she died, did Zeref revive her?
I sense a huge plothole while Hiro is trying to make the actual history.