I recently found out my mom had been cheating on my dad

I recently found out that my mom had been seeing an old friend from college (lets call him "J") and recently got invited to his wedding. She's been lying to my dad for roughly a year now and hasn't told anyone. I haven't had a chance to say anything to my mom about it besides "I'm not going to say anything" but I'm just extremely concerned. I don't think anyone would want to ruin their parents relationship. What do you think I should do?<br><br>EDIT: Okay so I asked my mom to come up and she's just recently shown me that it's for an old colleague's wedding. My mind has been blown to a million pieces and I felt like I was on a rollercoaster as I got up out of the chair. I'm extremely mortified but my mom is VERY relieved. Thanks so much for your kind words. I appreciate them!