This is a story from A Dream of Red Mansions. Third Sister You, a beautiful and strong-willed woman, was the sister of Jia Zhen's wife. Jia Zhen, a notorious playboy, grew tired of his wife and set his sights on Third Sister. He conspired with his cousin Jia Lian to seduce her, but she fiercely rebuked them. Frightened by her virtue and unyielding spirit, the two men sought to marry her off quickly.
Third Sister fell in love with Liu Xianglian, an actor who had once performed at the Jia residence. Her sister falsely told her that Liu had left the city. Undeterred, Third Sister vowed, "I'll wait for him, whether it's one year or ten. If he dies, I'll shave my head and become a nun."
Later, on a trip to the capital, Jia Lian met Liu Xianglian by chance and conveyed Third Sister's feelings. Liu agreed to the match and entrusted Jia Lian with his mandarin duck sword as a betrothal token. Overjoyed, Third Sister hung the sword by her bed and gazed at it affectionately every day.
Months later, Liu returned. Upon seeing Third Sister's beauty, he grew suspicious of her virtue, thinking, "The men of the Jia family are all promiscuous. Why would she love someone she's never met?" He fabricated a story that his aunt had already betrothed him to another and demanded his sword back.
Third Sister understood his doubts. Heartbroken, she took the sword from the wall, unsheathed it, and committed suicide before Liu to prove her purity and resolve. Overwhelmed with regret, Liu wept bitterly over her body. He spent the rest of his life as a Taoist priest.