Like the other ladies, I, too, hope that the forthcoming letter is an apology and a "reaching out" to you, to let you know she is sorry for the pain she caused. However, I think it's a good plan for your hubby to read it first and save you some agony, if it is a hurtful letter.
Praying that it is kind and loving, so as to ease some of the pain she caused you! I kind of think it will be, because of the mental connection you both seemed to have as her life was ending.
Love and blessings to you, sweet lady!