The crash of bowling balls knocking into the trash can unaccompanied by any animal sounds alerts Martha to the fact that the creature had not followed her inside. She slows and turns her head, only to see it turn away.
Wary of trickery, Martha grabs another bowling ball and stays in the alley, listening in case it comes in a different door.
She's good at staying still, good at hiding, and excellent at listening. After waiting long enough for the chances of a second attack to decrease, she finally drops the bowling ball and begins hurrying home. As fast as her bleeding self can run.