[She actually holds her breath as he speaks the oath, because if he's lying she has no doubt that he will be met with swift divine justice. It's to her great and obvious delight that he's not.]

Oh, wonderful! Now, that wasn't so hard, was it? I daresay this went very well indeed! I do have to wonder where the confusion arose... oh, but Rin--er, our friend will be so pleased to hear of this! You have put our minds at ease, Lord Baelish!

[She will just. Continue to believe he was joking about the brothels.]