Also very human for her to not tell Harry out of bitterness, blaming him for her predicament, not just being a half vamp, but pregnant as well.
How do you know it was bitterness? It is clear they never stopped loving each other. I see no reason not to believe her stated motivation, living around Harry is dangerous.
And a relation with a half vampire would be problematic. Problematic enough not to try it? You can disagree with Susan and still believe that is what she thought.
And now living around Susan was dangerous too. She saw it but she could not cut herself off from her child completely. That is how people are.
And yes she should not have taken that decision alone because it was not just her child but that is how a lot of women think and one of the reasons a divorce can be so problematic but the feelings are real. Which is totally different from the feelings are right.
Trust your feelings is not always a good idea.