Sierra watched Melaka's expression grow colder. To think about it, Fenris never said anything about that thing, either. The only people who spoke to her about that were Rodnir and Kanaru. No one else was supposed to know. Yet, Fenris never made a trip to explain the circumstances to her. She didn't expect Fenris to apologize… only because he was the king.
As for Melaka's case, Sierra figured she was closer to the real Fenris than anyone in the inner court. Melaka had been here even before Rodnir came into the picture. Whatever they had could have been real, but Fenris deceived her halfway through.
Then again, it couldn't be helped. Melaka couldn't get upset too loudly. Only the ministers and a handful of people knew. She couldn't lash out just like that.
It's not that Sierra thought Melaka would lash out, for real.