We are talking of maybe hundreds or even more wounded and dead and Harry feels guilty about it. He got them into it or accepted their help. He must have known many of them and he learned to know them better just before they died. Of course he is down, Molly is quite correct here but Molly wouldn't talk that way if Karen was dead because of him. That would have been far more dramatic.
Murphy doesn't have to be dead because of him.. What Molly did takes some of the pain away for all of those dying and getting hurt.. However that doesn't take away the personal pain of losing someone that close. It is hard to explain, Molly's gesture helps with Harry's pain/ guilt over the many.. However nothing is going to relieve him of the pain of loss of one or more of the three I mentioned. There is nothing dramatic she can do or say at this point in time, that is why the sisterly kiss. That speaks volumes..
She is saying, "I'm so sorry for your loss.." Because there are no words beyond that for the pain.
I think the reason Karen did not show up is quite simple and has nothing to do with her status at the end of Battle Ground and everything to do with Jim not wanting us to know what her status is. It is to prevent spoilers.
Again, possible, but I might also point out he pointedly warns about spoilers before we go to read it. That is my point, I think most of us had a good idea from what Jim has said the last couple of years that it was a given, lots of death and mayhem in Peace Talks, we didn't know about Battleground yet.. So no, he isn't spelling out who died, perhaps I am reading too much into it from personal pain from loss, but because of that, to me, the whole story reeks of Harry grieving and trying to carry on, and not over the thousands, but over the one, two, or three closest to him who are now dead.
We are only shown people who we knew would survive. I would not draw conclusions based on who was there or not.
True, however one can come up with good reasons why Thomas or Eb wouldn't be there, but not so much Murphy save perhaps she is so badly injured she is still in the hospital. However the personal condolences, even from Mab for goodness sake, says one or more of the above is dead.