it really wouldn't have been hard to show something in the way she saw and dealt with the world had changed after her time with the Doctor, even if she didn't remember him.
Exactly. *sigh*

"the old man prefers the company of the young", like the Dream Lord said—but indeed, Wilf was just wonderfully refreshing. Well, there's also something for the audience there, probably—same way they're doing young and sexy Doctors. But like you said, the audience LOVED Wilf ;)