User blog comment:IamJakuhoRaikoben/Chapter 388: Erza vs. Minerva, Review./@comment-24800928-20140614020234/@comment-7418318-20140614080601

Sacrificed her life? How so?

Erza beat her up so badly she can no longer stand. She wouldn't have been able to dodge Mard's blast even if she had tried.

And Erza Knightwalker was also a cold-hearted sadistic bitch. She might have followed orders, but she openly admitted to enjoying those duties. When she was about to kill Lucy she didn't say "sorry, but orders are orders". Instead she said "I relish watiching people suffer" (see here. The "See you Lucy" and her expression on the next page right before she tossed Lucy to her death makes it very clear to me that she was telling the truth. That wasn't just being deluded by loyalty or a power trip. That was straight out sadism.