Reborn to Serve My Heroine Sister

She is trapped in a reincarnation loop, and every timeline ends the same: her illegitimate sister becomes the supreme ruler, and she dies. Whether she sabotaged her or stayed away, fate always favored her sister. Reborn at the imperial selection once more, she changes her strategy entirely. Instead of fighting destiny, she bends the knee to become her sister's fiercest ally. But can she truly secure her survival by serving the future empress?