Two things... (1) I would give ANYTHING to get a letter like this from my mother. She is WAY more attached to me than I will ever be to her. My father (may he rest in peace) was a different story. My mother (and other mothers) build up SO much hope and expectation for something that is just never going to happen. They create their own "turmoil" because they keep projecting something that doest exist: hope their child will join them in the cult
(2) Any "pain" and suffering she goes through will be part of the martyrdom that all 'christians have to go through'. So in this case, she will use this pain as "proof" she is in the right religion doing the right thing for the right god. There is never any winning with this mentality. It's so sad the closed-minded tunnel vision and I'm sorry David had to get this.
(side note: being a witness IS easy. everything good is a blessing from Jehovah and everything bad is an attack from Satan. There is no thinking involved... all situations are on someone else's shoulders. This letter is a good example of the simplicity of their thinking. As sad as it seems... I personally am glad I grew up. My heart and love to David... it's not an easy letter to get.)