Remei Abello knows perfectly well that she's too attached to her favorite sister. 

The fact that even their parents can't tell Remei and Marta apart is useful, and has been since they were very small; the fact that they have a near-perfect ability to cover for each other; to give each other alibis when necessary, to divide their time however is most advantageous to them, gets them cooperating early. The two of them make perfect allies, because they know each other so well; because each of them knows that the other will be more than useful enough to make up for any inconvenience in being useful themselves. 

It's not, strictly, Asmodean; neither of them has ever crushed the other in any meaningful way; neither of them is superior or inferior, in the long run. Even when one one of them has a clear advantage over the other, they never press the advantage, never behave tyrannical about it in private. 

It's Remei Abello's greatest strength and her greatest shame. 

The two of them are sitting on the hill overlooking their village, spinning and quietly discussing how the government's overturn has affected the local social dynamics.