Do you think it's possible?

Do you think it's possible for someone to be in a relationship with someone who's having a baby with the person they cheated on you with? More specifically, my good friend is bisexual (has been in a relationship with a girl who hasnt always been a good girlfriend) who everyone thought was a full lesbian...apparently she just gave birth to a baby though. Her girlfriend (my friend) had no idea she was even pregnant. She claims she didn't know she was pregnant for very long either which could be a real possibility or could be total BS. In her defense she didn't look pregnant at all. Weird right? Anyway, my friend wants to stay with her and work it out even though this baby obviously came from being unfaithful. I don't agree that she should but it's not my place. I'm just worried she's going to end up resenting that baby eventually. Maybe not but idk. What's everyone else's opinion? Has anything similar ever happened to you or someone you know?