...she probably didn't care what their plabs were. She pressed them to stay because it fit in with her plans and since she is accustomed to getting her own way, I doubt that she would have made the offer without expecting to do it. If that had been the case, she might have said something like: "If you had not already made the ill-adivsed plan if going to see your sister in London, I could have taken you that far myself..."