You could say calmly: “I saw something I shouldn’t have. You have 24 hours to tell Dad, or I will.” This puts the responsibility on her, but only do this if you’re prepared for her to react badly.
Families can fracture. You might be blamed by her, or even by your dad temporarily if he shoots the messenger. None of that means you did the wrong thing — it just means the situation was already broken. i caught my stepmom cheating
Pick a private, calm moment. State facts, not accusations: “Dad, on [day], I saw [stepmom’s name] with [person] doing [what].” Don’t embellish. Be ready for him to be angry, sad, or even in denial. That’s not your fault. You could say calmly: “I saw something I shouldn’t have
I’m really sorry you’re in that situation — it’s a heavy and confusing thing to witness, especially when it involves someone close to you. While I can’t know all the details, here’s a proper, grounded piece of advice on what you might consider doing next: You might be blamed by her, or even