Could any of you help me find a movie?

Seeing the silhouetted image of a wheelchair during the opening credits of WOMAN OF STRAW, the fact that this film is a thriller & it's partially filmed on picturesque locales like Majorca, I got flashbacks to another film (surely made during the 60s, or early 70s the latest) I saw as a child on TV that I cannot remember the title or cast.

I wonder if based on the below plot points somebody can point me to the right film. Forgive me if I jumble some of them as it's been ages since I last saw it.

At the beginning of the film, the body of a young woman is fished out of the water by a big stick or something.
Another young woman goes to visit an "aunt" and her boyfriend. The area has many cliffs. The aunt is wheelchair bound. She has short blond hair in the style of Jean Seberg. I think the boyfriend makes a play for the young woman. At the end, SPOILERS BEWARE, it turns out the aunt & boyfriend had killed the woman at the beginning of the movie, and the other young lady that arrived at their place was that woman's sister trying to find out what had happened to her. The aunt had been faking her invalid state. She is sitting on the wheelchair at the edge of a cliff, the boyfriend comes running behind her thinking that it's the young woman sitting on it & kicks the wheelchair over the cliff, realizing too late it was the aunt (his lover). She falla to her death.

If anybody has a clue as to which film this is, I'll be eternally grateful.

:)