She's coughing again.
She always seems to be coughing. Everyone knows her as the sick kid, that poor child, that unfortunate little girl. People watch her as she quietly walks past. People whisper behind her small, fragile back. People give her fake smiles and false pity as she passes them, one by one. They all act friendly, but they never get close to her. No one will touch her because she might break.
She pretends that they don't exist. She can't see their disgusting smiling faces. She can't hear their cruel words. She can't feel their intruding eyes. They aren't there. They never were. They never will be.
She's coughing again.
She always seems to be coughing. She coughs at the worst possible times—it never fails. She feels the coppery red liquid drip, drip, drip from her lips. The surface of the rough ground scrapes her knees and hands as she crumples, trying to stop the coughing—the pain—the bleeding.
When she falls she falls alone, and everyone leaves her behind—even her parents. They save themselves. There's no point in saving her, after all. She's the unfortunate little girl who can't run as quickly as they can for fear that she'll collapse. She's that poor child who can't yell and scream like they can for fear that she'll start coughing again.
She hopes they die. She hopes that they feel what she does. She hopes they cough and bleed and splutter and feel her pain. She wishes them nothing but eternal suffering. She curses them with every shaky breath she takes in-between coughs.
The strange black shadows are advancing and she clutches her chest, spluttering and bleeding and suffering. She's dead. There's no one left to save her. She fell behind, and she was left behind. She looks up into the menacing yellow eyes that are drawing close to her, closing in on her, eying her tiny, frail body.
She laughs.
She laughs, spluttering at the same time, blood running over her lips and falling beneath her onto the ground in-between her shaky hands.
She doesn't scream when they finally descend upon her, claws drawn. She doesn't cry when they tear at her flesh hungrily, ripping her to pieces. She doesn't cry out when they mangle her frail body, tearing her apart, searching for what they seek. She laughs and coughs and splutters and bleeds.
She isn't coughing anymore.
When she wakes up, and her acid green eyes blur into focus as she takes a raggedy breath, she's staring at white walls and mysterious symbols and chairs that resemble thrones. A deep voice asks her for her name. Relena, she responds quietly, her vision sliding in and out of focus. There is a pause, and then she is given a new name; a new beginning.
"Larxene."
She doesn't cough anymore.
My take on why Larxene would be sadistic. It seems like she wants people to suffer as some type of atonement for their cruel treatment of her as a sick child.