User blog comment:Oknight/Artemis, Cheshire = sisters pretty much confirmed/@comment-3990752-20110905113325/@comment-173.66.189.214-20110910223055

And plus, All the assasins we've seen from the League of Shadows have an alias. Sportsmaster, Black Spider, and so on. Artemis probably didn't recognize Cheshire because she went by the alias Cheshire. It makes sense.