User blog comment:Omega natsu2/Chapter 365: Fairy in the Jail!, Predictions./@comment-112.203.211.177-20131219235849

I think Mira and Erza are faking being asleep considering Erza almost slipped up and called it "perfume" and considering he knew Ichiya who uses perfumes to varying effects this should already be a give away that something is off plus the fact that Mashima kept on emphasizing that they are the "most reliable two" last chapter and in this chapter then them being tricked would negate that title.

I think they faked being asleep to know where Tartaros' headquarter is and infiltrate it from the inside, just my hunch though.