After Becoming a Widow, I Married My Nemesis

Upon returning from studying abroad, the second young master of the Cheng family disdained his fiancée for being illiterate and firmly broke off the engagement. The woman married out of town in resentment and was soon widowed. A year later, they met in the business world. Seeing her speak English fluently with foreign merchants, negotiate business, and conduct scientific research, Cheng Zhiwen was puzzled. Who is this woman?

He secretly observed her and was unexpectedly attracted. Later, he was even willing to kneel humbly at her feet and ask, "Is our engagement from back then still valid?" She raised an eyebrow and glanced at him. "I've already killed one with my bad luck. Do you want to be the second?" Second Young Master Cheng replied, "Yes." Shen Qing said, "Get lost!"

...It was another snowy day, with snowflakes flying. A prison cart slowly rumbled through the busiest street in Jiangzhou. Shen Qing was being dragged to be beheaded. In the dark crowd, she saw Cheng Zhiwen. He had come to see her off on her final journey. She smiled at him through tears. The executioner raised his hand, and the blade fell. A head rolled to the ground.

When she woke up again, she was in a festively decorated bridal chamber. Shen Qing reached up to touch her own neck; her head was still there. A maid entered, knelt by the bed, and bowed. "Second Mistress, you are awake."

So, the question is, whose mistress has she become?