I didn't get the logic of Gibbs' "I walked away but we still ended up here (the cemetery)". She was going to be at "cemetery" no matter what. If she hadn't been murdered on September 10, she would have died on September 11 with the rest of her department. It was terrible that she was murdered but she still wasn't going to have a long happy life.
And, if you think about it, the fact that Gibbs walked away from someone to keep them safe and she died anyway (at the time he thought it was because of 9/11), that should have given him some perspective that life is going to happen and all he did by walking away was to spend less time with someone he loved. You would think that might have changed the way his post-her relationships were.
Also, what was with the weird turning the chair upside down and cutting off the feet? I get that he did it when he was alone in the interrogation room because the chair was wobbly but he appeared to do it the second time as an intimidation tactic. Really? Some high ranking officer who has been in combat is going to be intimidated into confessing to murder because Gibbs pulled out a knife and cut the plastic thingies off the bottom of a chair? It's not like Gibbs could stab him in the interrogation room. I thought it was stupid.