[She already knew that the ship was important, on many more levels than what she could imagine at first. But she hadn't thought that even as a joke it would be wrong, at least he knows that it was a joke, it makes her feel less horrible.]

I see... I'm sorry, Luffy. I would never do that, but now I won't even joke about it, I understand that it was rude and of bad taste.

[Even more so if the ship is considered nakama as well, had she known that bit it would have never even crossed her mind.]