Tim's a cartoonist: it doesn't surprise me that she's a sharper observer than most of faces and behavioural tics. And to my mind, Marie has the acute awareness of other people which can come from being bullied. It's an important security mechanism to know exactly who's around you and what kind of mood they're in.

Both Ann and Ginty are mainly fooled by Lawrie's acting, and don't even notice Nicola; and as someone said above, Miranda's skills aren't tested, because Nicola tells her as soon as they see each other.