When I divorced my husband of 12 years, I was so depressed. My friend Ava took me in. She saved my life.8 years later, I ran into my ex. The first thing he asked: “Are you still friends with Ava?” I nodded. He smirked.He said,  “So you still don’t know that she’s the one who ruined our marriage?”�I froze when he revealed that the woman he’d had a brief affair with—the one that led to our divorce—was Ava.It turns out Ava had felt so guilty...