User blog comment:IamJakuhoRaikoben/Chapter 518: Master Enchant, Review./@comment-4507125-20170122023520/@comment-1776824-20170122091643

It's not, "What is she..?" as in, "what is my daughter doing?" It's, "What is she..?" as in "What kind of person is she?" Irene is in total disbelief that her daughter is willing to risk her life to stop a meteorite, knowing that she's going to without a doubt die, even if she succeeds. To be clear, judging from just a couple pages back, Irene and the reader can clearly see that Erza is going to try and stop the meteor. Therefore, the latter interpretation is the correct one.