My Young Auntie (1981)

Cheng Tai-Nan (Kara Hui) is an honest and faithful servant of a dying patriarch who wants nothing more than to protect his vast wealth from his selfish, conniving nephew, Yung-Sheng.

Tai-Nan is young enough to be his granddaughter, but still agrees to marry her master so that all of his wealth will be lawfully safe with her so she can then transfer it to Ching-Chuen (Lau Kar-Leung), her new husband/master's favorite nephew. This angers the hateful Yung-Sheng greatly, who sends multiple thugs after Tai-Nan, but she is a highly skilled martial artist who is not easily defeated. Amazingly, things become even more complicated when Ching-Chuen's son, Yu Tao (Hou Hsiao), arrives home from a university in Hong Kong and discovers a mysterious women in his house and attacks her, not realizing she is actually his new great aunt, Tai-Nan. Complicating things even more is the uncomfortable sexual tension between Yu Tao and Tai-Nan. Next Yung-Sheng finally manages to steal all the paperwork, titles, and deeds to Ching-Chuen's wealth. Left with no choice but to lead an all-out attack against Yung-Sheng at his booby-trapped mansion, Tai-Nan decides to get Ching-Chuen and his older brothers back into fighting shape.