If I could completely erase my presence like that, I really would do everything in this castle myself. We wouldn't be having this conversation.

[She can mask her own mana, of course, but only enough to make her pass as an average human to those with the ability to sense magic. Nothing so extensive as to hide their whereabouts. If anything, she'd expect a ninja would be better able to pull that off.]

Anyways, it's not that big of a deal, just something we should expect and prepare for. This is a big castle. She can't monitor everything at once, so once we're there it will take her time to respond. If we work quickly, we'll set ourselves up for less trouble to worry about.