Woman has affair and kills lover she thinks south of France her and her girlfriend drop his body off and he is alive but has amnesia her doctor husband helps him get back him memory.

Moment to Moment (1965)
IMDb review:
Jean Seberg plays a bored housewife and mother vacationing on the French Riviera with her neglectful psychiatrist husband (Arthur Hill). While he is away on one of his frequent long business trips, she drifts into an affair with a hunky sailor (Sean Garrison). As they motor around the area taking in the sights, they're accompanied by one of Henry Mancini's catchiest title songs. In fact, it is played so often that at one point she asks the bandleader at a café the name of the tune. He, of course, replies, "'Moment to Moment'." After a bad lovers' quarrel, she accidentally shoots the sailor, then she and her neighbor (Honor Blackman) drop his body in a nearby ravine.

However, he isn't dead and shows up in the company of her husband, who is treating him for amnesia (as I recall). She has to wait in fear that he will remember and "let the cat out of the bag".

Moment to Moment (1965) - IMDb (http://www.imdb.com/title/tt0060711/)