My bestfriend [25/f]cheated on her boyfriend with our boss[40/M], now I’m on a work trip with his wife. I want to tell her. What would you do?

My best friend and I used to work at the same place and while we were there, she cheated on her boyfriend of 5years with our mutual boss. She didn’t tell me this until after I quit. Now, I work with his wife at a different company and we’re on a work trip together. While I worked at the company, he constantly talked shit about her and how much they weren’t a good fit. Now that I’m spending time with her, she speaks highly of him and how she loves him, leading me to believe she doesn’t know he’s a piece of shit. I can’t risk causing drama at work and losing my job, but I want to tell her anonymously. I hate that she doesn’t know who her husband really is. I’ve told my friend she needs to fess up, but she won’t. I feel like I’m awkwardly caught in the middle and have no idea what to do. Would you tell her?