User blog comment:Omega natsu2/Fairy Tail Zero: Night of Embarking, Review./@comment-24546844-20140915011055/@comment-24039250-20140916003331

Technically she is a teenager not a child, and she doesn't die until about 7 years from now since that would be around the time Hades becomes guild master and Makarov is supposed to be the longest running guild master (48 years). X736 is when Makarov became the master and Fairy Tail started in X686. She will likely die in 7 years since Mashima loves 7 and it would make Hades leader from X693-X736, somewhere around 43 years. Yuri is likely not the master because he blames himself for some reason for Mavis's Death, and allowed Hades to become leader.

I also have a feeling that Mavis knew that she was going to die (my theory is that it was Zeref) and Yuri knew about this. He likely tries to stop her from walking to her death, but fails. Yuri seems more like the kind of person that should have been leader, but when he felt that he couldn't protect his Master, he refused to be the leader and Mavis picked Hades as the second choice (obviously, since I don't think Warod could be taken seriously as a leader).

As to how she dies, I think that (after seeing Ch. 340) after meeting Zeref at some point in the future, she begins to care for him and wants to help him,so she allows him to stay on Tenrou Island where no one can ever find him (except FT members....and Hades 40+ years later). In the end she will dies by his magic (Mavis embracing him while he cries (I have always envisioned this being how she dies)), and stays behind via Ethernal form as a means to watch over the dark wizard until the day comes for someone to save him (Natsu Dragneel).