Sementara b inggris ya.
Riel(Rielle) grew up with the knowledge that her sister will always serve her and be dismissed by others (esp. parents) and i remember reading the translated prologue that Irene's friends got angry at her because they think that Irene was 'bullying' Rielle and Rielle only response is that it should not be a problem or so and then we see Rielle started becoming those girls friends.

Perhaps Rielle may have been really sick when she's younger but as she grow up and saw her environment she just learned that it is natural to put down Irene and took everything from her. After all, their parents did that and so Rielle did the same thing, except now she outright lie and manipulated people around her