User blog comment:FairyRaven/Fairy Tail Chapter 324: The One Who Closes The Door, Review and Commentary/@comment-2214433-20130322143654/@comment-5161856-20130322151224

Bottomline is that if the the creator wants a character to die. No matter how he/she dies, the character will still die. An excuse of overusing her power could be a good reason for not healing Future Lucy since they were fighting the Hungry Wolves and some guards earlier..

May she rest in peace.