Take a deep breath Janit and let it roll off your back! God I know it's hard, but it's almost over now.
Blame is useless .... you will never make her see it the way it truly is and he is her son, she will love him always and probably never see his faults.
You can write her back and say nicely that you appreciate her insight and obvious caring and thank her for taking the time to put her thoughts in writing to you. You might also add that you'll ask the kids call her as soon as things settle down.
Stop the cycle Janit, only you can do it at this stage of the game. You can take the bait, or decide you're simply not into that sort of bait anymore!