The Lady Hermit(1971)

A young Kung Fu student seeks a reclusive teacher so that she may learn to defeat the evil Black Demon. She doesn't realize that the servant woman she befriends is actually the kung fu master she seeks. After Black Demons henchmen attack, the master reveals herself and eventually takes on the student to train her so that they may both defeat the villain. A love triangle complicates things when another student asks for training as well.