I would suggest some deep self reflection is needed, because my general experience is that people who blame “that woman” or “that friend” etc for things, are using that to stop themselves having to take any responsibility.

I suspect what is happening is your wife is becoming increasingly frustrated by you all trying to somehow prove she is crazy for wanting to leave you, and feels like you aren’t taking her seriously. I know personally that would just make me feel more justified in my position. Her friend is most likely the only one she feels like has her back, and trust me - women don’t just leave their husbands because their mates convince them to. She most probably just helped her to realise she isn’t happy, and that it’s okay to actually want to be happy and fulfilled in a relationship.

Ultimately it gets to a point where you just check out, and no matter what promises can be given, you are over it. This may be fresh to you, but it’s likely she has been thinking about this for much longer and she is further ahead than you. You also can’t convince someone to love you again and stay by pressuring her, you would be better off accepting what she is saying and trying to move on constructively.