For Women Who Want The Ballerific Life!
Ok questions.... you said you two weren't exclusive & discussed the people you were openly dating and you were cool with that set up, right? So had he told you that he had someone serious, would you still be inclined to tell her that you're seeing her man? Is it the fact that he kept you in the dark about it that's upsetting you?
Honestly, i don't think that your desire to tell is to help her, I think its just to F**k up the happy home you think he has.
If he has other side pieces, I'm sure she already knows about at least one of them, & your telling her would just put a face to the thought and invite drama like someone else said. If you weren't trying to be exclusive I say just Curse him out and move on, no need to bring her down, because you got your feelings hurt.
Thats just my take one it.