Just like her hubby, Procris isn't the most trusting partner. In most versions of the story, Cephalus is totally faithful to his wife, but when a local busybody tells her that he's out in the woods cheating on her, Procris can't help but go spy on him. How many times have we seen this in the movies—and it never ends well.
What was that about it not ending well? Oh yeah—Procris dies. At the hand of a gift she herself gave her husband. Oops.
So in the end, Procris's suspicion leads to her undoing. And we have to say, it's not the fairest scenario on the planet: when Cephalus doubts his wife, he ends up getting some awesome presents from her, but when Procris has doubts, she meets her doom.