My wife would have been so lucky to have a friend like you. Also you should feel honored that she would feel comfortable with you to come to you. I am not sure what you should do but you are on a thin line. You need to somehow help her work through this at the same time you need to be careful you don't push her away by not saying what she "thinks" she wants to hear from you.. (Ya you are right leave your husband). Too many of the spouses here have "friends" that enable them to make the wrong choice. I don't think they do it on purpose, but they just want to help their "friend" and tell them what they want to hear. Maybe you need to try not to "Tell" her stuff.. But ask her questions to make her think more about what you know / feel..
"Do you really think your husband would be willing to try again?" "Are you moving to just get space or is there someone else"? "How do you think this will affect you son?"
IF you feel comfortable with it you might want to tell her some of the stuff you went / are going through but only as much of it as you feel comfortable with. There are some things that even after all the "C@ap" we have gone through that I think needs to be kept between a husband and wife..(At least while still married).
Don't know If I confused ya more or not Talk to ya later Doc
And if I claim to be a wise man, well It surely means that I don't know