The very existence of Hava should turn Bitterblue's stomach.
Normal children are repulsed, she thinks, when they find they have half-siblings. In order to create that life, there was terrible sin on the part of one of their parents against the other. She and her Lienid family should be outraged on behalf of Ashen.
Bitterblue cannot separate this reality from the reality that her father was Leck, and that both Hava's and her mothers were raped. In Leck's case, matrimony barely mattered.
It is selfish of her, but Bitterblue is grateful that someone else in the world knows and shares her painful legacy, in a way. While Hava will never have to rule a kingdom, she cannot escape the simple deceit that is her Grace.
Fire is almost as close as Hava. Bitterblue senses that Brigan, too, would understand. But their fathers ruined a kingdom and countless people through neglect and carelessness, not by pure selfish madness. The effects of their fathers were political, not emotional.
But as much respect as Bitterblue has for them, she suspects the emotional massacre Leck left behind in just a few minds is far worse than the state of the Dells. But either way, they are old and have finished their grieving, if one can ever finish such a thing.
Bitterblue almost feels, on the bad days, as though her grieving begins anew every time she learns something that she knows is the truth.
She knew it in her blood and bones from the moment when she discovered Hava's identity: there is nothing half about Hava being her sister.