I just did the Marton quests again and for me it doesn't make sense to have her there. We defend HD before we continue to Isengard where we meet her and she gets her name. Do I miss something? Are we at a point in the story where HD is over and we go back? But that would interrupt our journey with Bingo. Please help my confusion on this point. I'm eager to see an explanation why Mercy is there. Don't I have the story memorized correctly?