User blog comment:Rassilon of Old/Silhouetted characters on the Young Justice: Invasion poster revealed!/@comment-3511850-20120609160929/@comment-96.241.72.70-20120613211443

It's certainly a possibility, as Brandon's hinting one of the characters shown isn't a regular in the series. If that's the case, she might have been recruited to fill in for Artemis during her retirement. Or, it's Artemis heself.