Asking for my bestfriend.

Please dont judge. My bestfriend wanted me to post this on here. I dont want to get into her buisness & maybe I should stay out of it but I told her I'll ask.

2 years ago while she was in a relationship with her boyfriend she cheated on him with another guy. That guy as well had cheated on her gf who was pregnant at that time & she had trouble accepting the pregnancy. Eventually my bestfriend cut off that relationship knowing it was wrong. It's been two years. She found out the girl is pregnant or had another baby already. Shes feeling guilty, she said she should have came clean & tell the girl the truth. I dont know what to tell her or any advice to say. She asked me if this happened to me would I want to know & I said yes but its been 2 years. If she tells her now she would be heartbroken & it could definitely break their family. What advice would you give her?