Should I expose the cheater?

Dear Sex and the Shtetl,
I'm a single woman in my 30s and my cousin is also in her 30s, but she’s married. Last week I saw her husband on a dating app. Should I tell my cousin?
Reclining (and swiping) left

Dear Reclining (and swiping) left,

Oh the tangled web of modern dating apps, shtooping and shtetl dynamics. First, let me say, finding your cousin’s husband on a dating app is a moment that no one prepares you for. It’s like seeing your high school Tanach teacher at a rave or discovering your financial advisor moonlights as an Uber driver; it’s jarring, awkward and full of questions you’re not sure you want the answers to.

I’ve actually been in your situation before (minus the cousin, but substitute a close friend and their slimy spouse). Years ago, I caught my friend’s husband in the wild trying to lure one of my work colleagues into his pervy den. I felt like a character in one of those moral dilemma psychology experiments. Imagine the dramatic voiceover: Should she tell her friend and risk the friendship? Or stay silent and let her friend live in blissful ignorance?

My mother, the eternal Kibbitzer, surprisingly tried to convince me to stay out of it. She too had been in this position before and breaking the news ended her friendship as the friend forever associated my mother with the trauma of discovering her cheating husband. “Stay schtum” my mother whispered, too loudly, in the women’s section of our synagogue. “Shhhh!” came the chorus of daveners. 

Did I stay silent? No. I’m not built for the quiet torture of knowing something so explosive and doing nothing. So I confronted my friend’s husband then? No. I am conflict avoidant. Did I tell my friend? No again, I’m a full blown ‘Zitser mit tsitern’ (sitter with shivers). Instead I opted for a compromise: I told my friend’s brother and let him decide how to handle it. Did it protect our friendship? Yes. Did I feel better knowing I’d done something? Yes, though only after several glasses of sacramental wine and a week of anxiety diarrhoea.