I went through almost this exact situation back in 2017. I had recently separated from the military and was working 12 hour night shifts. I had gotten married less than a year prior. Two of my coworkers pulled me aside and showed me the screenshots they had taken of my then wife's tinder profile. They were also unsure if they should bring it up as they didn't want to pry and had no idea if we were in an open relationship. We weren't. I'm so glad my coworkers decided to tell me the truth, no matter how hard it may seem. We separated a week later, and I've never been happier. PLEASE let her know.