He starts a little when she makes herself bleed, he's still not used to that being so important.

"Don't! You needn't... her blood is the same color as yours. And please don't ask how I know."

He would rather not bring up the last time he saw her dead. But now that he knows this troll is more or less her identical duplicate he can make a safe guess as to what she is. He knows two other similar pairs, it isn't hard to put two and two together to get four.

"You're older than she is, from before her time. You wouldn't know her."