Her son is dead. No mother should out live their child. Even if that child was deeply flawed.
Clay is on the run. The two FBI agents won't say anything about what Derek did to get her elected.
Maybe, they think she's suffered enough or perhaps someone behind the scenes had scared them into silence. She no longer cares about any of it.
Jessica hadn't known what he was up to. Maybe she hadn't wanted to see it. A mother's love can be the blindest form of love.
Every time she goes to tell the truth the words won't come out. She wanted the world to know. Jessica wanted the sympathy to dry up. She craved the judgement of her parenting, she wanted every failure laid out bare.
If she had spoilt him less, adored him less, fixed his fucks up less he might have been different. Sometimes she gets letters and emails. Parents who understand the loss of a child. She has to fight the urge to reply to them, telling them that it isn't the same.
Because their child or children had good in them. Derek didn't. There was nothing redeemable about her son. That is why Clay had let her live. To live with the knowledge had her son lived he would have hurt more people. His death was needed to save others.
That was the worst punishment he could have inflicted upon her. Knowing that her son's death benefited the world.