Lower face: Take away all the obvious physical attributes, and you can see how she holds each character to her own even when it comes to the subtle attributes.
As Alison, she holds it firm. So much, that her very obvious chin kind of just paths itself with the rest of her jawline.
As Helena, she hold her lips a little loose, giving the movement a sort of ease.
As Sarah, the right side of her lower face is slightly crooked, making a dip right around the lips corner. Also when she talks, the left side of her lower lip juts out a bit.
As Cosima, she seems to put most of the pressure on the lower lip, and uses mostly the part under it, keeping the upper lip in place.