Resting Bitch Face
Just watched all 6 Series of GOT in the past week (very late to the party I know!).
I remember Lena from Dredd and 'The Cave' and thought she played a bitch looking baddy really well in in Dredd!
In real life I do think she does have a slight natural 'Resting Bitch Face' but in GOT especially (as Cersei), she has perfected the art of how a woman character should scowl and look down on others if the character is supposed to be a 'bitch'.
In fact she does it so well that in real life I imagine everyone automatically assumes she is a bitch!