She had to fight to keep back a laugh and instead stuck to character and got all brusque. "Right then, you better prove to me what yer sign says is real, or else I'll be havin' the whole board o' inspectors descend on you en masse!! Chop chop!!!" hand chopping motions, and she did laugh as the Doctor whisked her away. Younger or not, still the Doctor where it mattered most.