I often write letters that I never intend to send just to unburden myself.
Losing an unborn grandchild hurts whether it was miscarriage or abortion, she allowed the gf to make that choice - she can still be sad about it though.
I don't get that she is overly protective of her son, the need to be protective doesn't diminish just because they are grown, you just have to learn to quash it, and if this helps the writer to do that then why not?
She didn't paint the gf too badly or hint at her identity even if she does write like a would-be novelist and she ended with wishing her well.
As for her son, he may have been devastated at losing his child - why should he be obliged to participate? This is not a couple that agreed to abort or a man that forced his ex into a choice she didn't want to make; it was a woman exercising her right to make decisions over her own body, I totally agree that she should have that right but I'm still able to understand that this might be painful to the partner and I actually think that any woman who is considering this and has no intention of allowing her partner any say in the decision, ought to consider if it wouldn't be kinder to actually say nothing.