From the slight tilt of his head and the solitary crease on his forehead, she knew he wanted to protest her command. By the vow he'd taken and his silence in spite of of his obvious concern, she knew he'd obey. In the letters exchanged during his absense she tried to explain her reasons, her fear for her people, but he'd brush it off or completely ignore the half apologies.
When she'd chosen him, a foreigner, as her Lord Protector, there had been widespread gossip and not-so-subtle outrage. When he stopped assassinations attempt after attempt, the whisperers turned to the reason for his loyalty. The truth was never what they'd expect. Her (small) list of lovers had never included him, a stipulation that had been a private part of their accord. It had been his only condition to accepting the position, and one that she had readily agreed to; there was enough complication in her life without adding her romances to it.
The night her last lover broke her heart, he stood by her side. He offered neither criticism nor comfort, but merely waited for her to speak. She finally fell asleep that night with her head on his shoulder, having sobbed until her voice broke and her tears ran dry.
He was the first person to greet Emily after herself and the midwife. It was the first time she saw him smile genuinely, and she wondered what might have been if she could have allowed herself to fall for him instead (as all the rumors insisted had already happened). He became the best father to her child she could have asked for, despite having no obligation to do so, and in direct defiance of the whisperers. They raised Emily together, and though they'd never lied to the child about her parentage, she insisted on calling him "daddy" once in a while.
This was how she knew, as she took her last shuddering breath in his arms, that she could count on him to take her place as guardian, guidance, parent, and friend to the daughter she was most abruptly torn from.
Corvo Attano would not fail his charge. Jessamine fell into death's embrace peacefully, armed with that knowledge.