I hate/love this chapter so much...Gray would never die a pointless death,if he does I am going to kill Mashima. I hope Gray gets revived and guys,I support that Gemini theory if you know what I am talking about...If not,here it is:-
First of all,we all know that this show is about power of feelings,right? Feelings can make you stronger. So my theory is that Levy sent a letter to F-Lucy and F-lucy wrote a reply/summary of it in her diary which current Lucy is reading.
Gray's name was among the people who were dead in that alternative future so Lucy gets shock at first but soon thinks of a plan to help Gray.
My theory is that she has summoned Gemini and have them copy Gray so the one who died are actually Gemini(spirits can't die,they just get transported to their world for the time being). In this way,she saves Gray.