I am so so sorry for the loss of your dear mother..I know how you feel, my precious dad lost his battle with LC because of radiation pneumonitis.. His radiologist would not discontinue his treatment because he said there was no way he could have pneumonitis because it usually doesnt occur until weeks or months after treatment..Well, he was wrong my dad developed it during treatment, my dad stopped his treatment on his own against the doctors wishes..
What I really wanted to say is I know the devastation this is bringing to you, its hard so hard to think over and over in our heads what could or should have been done differently, our thoughts take us to places we would rather not be...
I struggle still every day accepting what happened to my dad, time has helped a bit however the wound is still there.. When I was reading your post I could feel the pain you are in and just want you to know I understand and hope you can find some peace and somehow begin to heal.....