Two coworkers (25F & 35M) are having an affair. How can I inform the wife?

I (25F) work as a receptionist. Four months ago, I made the stupid decision to recommend my (now former) best friend "Jane" (25F) for an open position after someone had left. It's a prestigious hotel, so they are very selective about their hiring process. Jane had little to no experience, so I took a risk by vouching for her. Looking back, it was dumb, but I knew she was a hard worker and I could've never guessed what was to come.

I trained her during her first month, and she picked things up quickly. After that we began working separate shifts. It was around this time that I started noticing a weird dynamic between her and "John" (35+? M), our chief receptionist. One night when I arrived for my shift, I found them acting all giggly and their body language just seemed off. They didn't notice me at first, but when they did, they tried a little too much to act cool which raised some red flags. There have been too many similar situations over the months, but I tried to deny it. John just had a baby, and his wife comes at least 4-5 times a week, sometimes with the baby too. Jane sees this as well, and I just couldn't think she would do something like that.

But the awkward tension, quick glances, and giggles just wouldn't quit, so I brought it up two weeks ago when we were out for drinks. I was floored by her response. She confessed in a playful manner almost like sharing a dirty secret. She said they couldn't keep their hands off each other and that she had wanted to "spill the tea", but didn't want to involve me in the "drama." When I brought up his wife and their newborn child, she said she didn't care. Apparently John told her they had been sleeping in separate beds, and his wife stopped caring about the marriage after the pregnancy, and other bullshit like that.

I was disgusted and we had a major fight. She stormed off and cut all contact with me. Since then, going to work has been hell. John is in charge of our shifts and ever since our fight, he's been giving me the worst shifts and making sure we're not scheduled together.

I've considered telling the wife since day one, but I don't have any proof. Same with our manager and HR. I texted Jane saying, "Tell your boyfriend to stop giving me the worst shifts," hoping for a response that could serve as evidence, but she didn't reply.

One week ago, someone got sick, and I had to work with the two evil fucks. Close to our lunch break, John's wife came in to bring him lunch. She looked tired as hell too, and my heart broke for her. Then I noticed something on John's wrist. He had Jane's scrunchy on his wrist (he also has long hair, but I know for a fact it's hers). He held and kissed the baby with the fucking. scrunchy. on. his. wrist. I legitimately thought I was gonna throw up. I had a panic attack (I think?) at the smoking area. I was crying and couldn't breathe.

I come from a divorced family because of my father's infidelity, so this hits too close to home. I am losing sleep. Please tell me what should I do in this situation? Should I send the wife an anonymous message? I only have her Instagram. I feel like I'm losing my mind.