It's a small comfort. If they'd been there for any length of time, she ought to have known. The truth was that in her haste she'd simply failed to account for them as any sort of threat. She'd underestimated their ability to kill a dragon.

And she'd underestimated Cersei's sheer cruelty, besides. There had been no benefit to killing Missandei. She gained nothing at all but a false sense of victory that would be all the sweeter to rip from beneath her.

"You had a duty to the Night's Watch. I had one to Missandei."

And to the rest of her people, besides. To the Seven Kingdoms. She had to win, whatever the personal cost, or she'll have failed them all. Take Cersei Lannister off the throne and survive to lead her people out from under the wheel that had crushed them for generations. It was the only thing that could begin to pay for Missandei's life, and her friend's last wish had been clear.