Shoot the messenger... WWYD?

[Goandplay]

At the beginning of DC starting primary school a mum from the class had an affair with another dad in the class. The married couple broke up and the couple got together and have been together ever since.
There is a lot of bitterness from the ex partner and everyone knows in the playground.
Fast forward 6 or so years the couple that got together following the affair have decided to get married and are planning a wedding. The bride to be is obviously excited and you can see the excitement and plans on FB with tags at venues etc.
My friend is close to the ex wife and she has shown text messages from the ex husband (I hope you're all following who is who - feel like a flow chart is needed!) that are at best flirty, at worst the beginning of something more. Ex wife has said she will take revenge when the time comes by sleeping with him and telling the other woman.
I feel bad every time I see how excited the bride to be is, I'm friends with her and the children are all going to be hurt when this happens, obviously IF it happens...
There isn't anything I can do though is there?

Personally I'd need more firsthand evidence to justify saying something.

The ex-w sounds bonkers.
Keep out of this. It will not end well.

The texts were along the lines of whether she was wearing underwear and what type and how good she looks in the underwear

I know it's a case of what comes around goes around but the women aren't strictly at fault here, it's the man. He is the one making promises and relationships that he's not keeping. Surely if it was that he fell in love and that was the reason for the marriage breakdown then I can understand but to knowingly go around causing this upset? Why would you put yourself, the women, the extended families and children through it knowing how bad it will be?

Your friend had an affair with a married man and is now marrying him?
If she is so deluded to think he'd be faithful to her when he wasn't to his ex and with her, I'd certainly wash my hands off it.

I'm by no means justifying the woman here. I'm stressing the point that he is responsible for keeping his vows iyswim?

Yes, he is. But the main reason I wouldn't enter a relationship with a man already in one is that I wouldn't trust him.
Your friend chose to trust a cheat. I doubt she'd even believe the texts.

Yes. I agree. It's not stable foundations from the beginning.

The fiancée won't believe the ex-wife anyway and he'll get away with it.

Well this is becoming more and more like an episode of a soap opera everyday. Something to do with the wedding was cancelled so I texted and asked why. BTB text back they'd broke up and luckily within a very short time to say just a joke they had changed the plans!
I could've easily have put my foot in it!