In the writer's letter she referred to her father's new wife as a "gold digger" FIVE times! It is obvious that she has some definite built in ideas on who this woman is without having ever met her or spoken to her. Was it wrong for her father to have an affair & run off with another woman? Of course! But that is what he chose to do and only he, his ex-wife (the writers mother), and the new wife know the full truth to the story of the affair & divorce. And those are the only people who need to know.
Kids like to think (even when they are all grown up) that they know every little thing about their parent's lives because the only function of the parents is to completely cater to, and submit to, the kids. "What? My parents actually have thoughts of their own that do not involve ME?! I don't believe it!"
The writer has implied that she is the poor suffering waif who was cast aside by the cruel step-mother and whipped father. She never mentioned how her mother may feel, because it's "all about" the writer being sad & dismayed. On the other hand, who did she learn about the affair from- her mother? Could it be that the mother is milking this whole ordeal as a way to garner more sympathy & further manipulate her grown children- maybe similar to how she manipulated her husband? I am sure the father has a completely different story than the mother & the new wife has her own version.
I think the daughter needs to get over the fact that her parent's lives are not hers. If she had her own life she would be raising her own kids, taking care of her own husband, and strengthening her own contribution to the world and not spending all her idle time boo-hoo-ing that her fairy tale is not ending with her pushing the witch into the oven. While everyone else in the story has moved on to brighter kingdoms, she is still tossing bits of bread crumbs hoping daddy will find his way home to her.
Her kids don't need a grandfather as much as they need a mother who is not wringing her hands over things that are out of her hands. If they have a healthy relationship with grandma, then that is all they need.
Spouses do not leave a "wonderful marriage" to run off with a freak. People, unless mentally ill (and that's a whole other ball game), do not leave a healthy home for the skids. Human instinct is to trade up. Maybe the new wife traded up when she landed Daddy. But he did not go unwillingly. Perhaps he, too, was trading up.