User blog comment:FairyRaven/Fairy Tail Chapter 327: My Part Too, Review and Commentary/@comment-7841492-20130412131019/@comment-7418318-20130412133810

The last time I checked people afflicted by amnesia had no way of choosing what to forget....

As for her purpose of coming, she herself said she had no idea of what to do and only came to warn people. And she did already serve two purposes in story. She saved present Lucy's life and she made Jellal go to Dronbolt and Lahar for the mysterious favour.

And on top of that it provided Mashima with a way to kill a main character without actually killing it.