The Thorn Flower's Vengeful Marriage

The Thorn Flower's Vengeful Marriage summary:

Juna, who had been secretly involved in wicked deeds to put her beloved Arendt on the throne, was betrayed by Arendt and his stepsister, Elena, when she had defeated all her enemies and was sent to the guillotine—
Awakening as her 10-years-younger self, Juna vows to make them pay! To seek revenge, she uses the natural magic she had been hiding and visits Arendt's older brother, Clavis, to propose marriage. However, Arendt was the man whom Juna had driven to his death in her previous life for a crime she did not commit.