Yoona fell in a swoop at her grave hurt and her husband's reaction. She didn't mean any of those words but it was still superficial to letting him know she not might bear his child as he was looking forward to having a son with her.
The old lady had listed the price she had to pay for having magic in her blood and yet she went ahead with it. What was the point of having children at the expense of watching her world crumble and her children being slaves to dark magics and evil lineage of Kigal. She wasn't gonna choose her happiness over the world's safety, Daejong had other women who would give him heirs and she would make certain of their legitimacy.
In refute of the old lady's claim, she had sought the medical assistance of Physician dong who assessed and confirmed her womb may not hold forth a seed as it was too hot. Her womb was hot!
