What is the importance of Rosa in this book?

Rosa

Also known as "Rosa the Beautiful," she is Clara's older sister and Esteban Trueba's original love and fiancé. She is born with a mermaid-like beauty, with green hair and luminescent eyes and skin. She dies in place of her father, Severo del Valle, from poisoned brandy left by his political adversaries. Years after her death, Esteban Trueba illegally exhumes her corpse and buries it alongside Clara's. The short story of Rosa the Beautiful gives us a first insight into the unusual, mystical qualities that surround the novel's main characters. Rosa is born looking like a mermaid, a creature of fantasy. The fact that she is born with her ethereal traits makes it clear that an otherworldly nature is ingrained in the characters, not just visited upon them. Rosa's story also introduces the theme of violence and suffering. In the world of the novel, "sorrow, blood, and love" are inseparable and interdependent. Accordingly, Esteban Trueba's first love is surrounded by death, both his lover's and his mother's. In the same vein, Rosa's beauty is marred by the violence of her autopsy and subsequent molestation by the assistant. Rosa's death marks the first time in the novel that one family member pays for another's crimes. Rosa dies in place of Severo, killed by his political adversaries. Later in the novel, Esteban García will rape Alba to avenge his own grandmother's rape by Esteban Trueba - a cycle of love and violence that Alba understands will continue for eternity.