User blog comment:Miskos3/Fairy Tail Chapter 505: Trump Card, Review/@comment-4449950-20161007232427/@comment-7418318-20161008175303

Zeref had a lot more time to regenerate since his fight with Natsu happened before Mavis was even out of the crystal, if I'm not mistaken.

Additionally Zeref was in the middle of his army and their supplies when he got hurt, so there's been a whole gaggle of hangers-on and retainers to clean him up and replace his damaged clothing, while Mavis on the other hand fled into the wildernes with just Mest by her side after being hurt. Additionally she didn't have time to clean herself up, what with the war going on all around her, so any bloodstains left on her skin would naturally still be there, even though the wounds underneath are already healed.