Will felt a glimmer of hope, if she was asking then she might not actually know.
"I thought everyone had already heard! My father and I came to a rather large political disagreement. He insisted the country should move in a more aggressive direction, and that the economy would benefit from conquest. I disagreed. As one of his sons, I would have lead such a military campaign, but I refused. So he disowned me; what good is a useless son?"
This was the public reason, and he was surprised she hadn't already heard it. It wasn't the real reason for his disownment of course. The real reason was the secret he feared she knew. It was something that, if it got out, would ruin his life.
Her response might allow Will to figure out if she truly knew or not.