I wouldnt even bother to tell her..

Let her find out herself..

2 reasons in my thought process for this

1) - she doesnt respect you.. How do you think you will look to her, if she knows you know about the affairs... and still want to try

2) - She has eaten cake from day one.. I dont believe this is any different... If she is accepted into this thing, she is still lying anyway ( or more than likelly ) - and you keep detaching / walk away.. She has an agenda.. or maybe its to say "oh kids mummy tried " etc

just MHO

Previous username - Helpme123.. A name chosen at a desperate time..

Now Mr Brightside.. coming out of my cage, and doing just fine.