Did the Elder Steward know?

I've just got round to finishing Dark Heir and have been reading the discussions but I've not seen anyone mention this - did the Elder Steward (and by extension, Grace) know that Will is the Dark King?

The way she phrased things and the way she acted made me feel that she did, and that she told Grace because Grace has also been very shifty and mysterious so far. She also mentioned something about how the attack on the Hall wasn't their darkest hour (from Dark Rise):

“I thought in their darkest hour the king was supposed to appear. Isn’t that what Stewards believe?” said Violet bitterly. “That they’ll call for the King, and the King will answer?” Grace was looking back at her strangely, as if the words sparked something internal. But: “I asked the Elder Steward that,” was all Grace said. “Sarah was with me. She cried and begged. The Elder Steward said it was not yet time to raise the call.” “Why not?” The flame light on the empty battlements leaped and fell, high and red. But beyond it the night stretched out, endless shadow that covered all the land. “Because this is not our darkest hour,” said Grace. “That is still to come.”

The Elder Steward also says:

“I think there is great power in you, Will,” she said. “And when you learn to wield it, you must make your own choices. Will you fight with strength, or compassion? Will you kill, or show mercy?”

Surely she must have known Will was the Dark King reborn? And she also had some idea of the events to come. And by extension, Grace probably knows some of these things too so the question is, what will Grace do now? Grace feels like the only one acting to "the plan" (whatever that may be) and not just based on emotion like Cyprian and Visander. I wonder also if this is why Will told her to take charge if something were to happen to him.

The Elder Steward seems to have put her trust in Will doing the right thing, and her influence is still there in Grace and in that projection stone, which for me is a bit of much needed hope after that emotional bombshell ending of Dark Heir!