Her Name Was Ellie, His Name Was Lyle(1967)

In New York City, a relationship is threatened when a young man discovers he's caught syphilis from a tryst with a waitress named Ellie. This threatens his relationship with a new girl. Film critic Amy Taubin co-stars as the new girl who gets the bad news. The director is apparently the same man who edited Fritz Lang's The Testament of Dr. Mabuse.