I think you should advise your dad to NOT send a letter. Nothing good will come from trying to tell her that she's wrong. She's following her feelings, and when you tell a woman that her feelings are wrong or invalid...well, you might as well tell her she's stupid! That's just the way it works!
Off Topic - Your screen name....do you play Blues or just a fan?
Me - 47
WAW - 41
Married - 9-14-85
Kids - D14 and D12
Bomb - 1-19-06
W moved out - 5-29-06