The Praying Mantis.

Trixi Jancik leads a risky double life. At home, she is an obedient housewife. But when she puts on a disguise and goes to the racetrack to indulge in her secret passion, she catches a glimpse of a better life. Although she blows her grocery money, she has tasted the kind of luxury she can normally only dream about. A minor squabble at home brings the situation to a head and marks a turning point in her life: Trixi fixes her husband a lethal cocktail of pills.