Hi bob, I have to make this very quick. I just want to point something out to you. I do understand your frustration! however losing it and blowing up and fighting is letting your emotions take control, I know its so hard not to do that sometimes however this is what happens with her when you do.
She feels you dont understand her or care about her feelings or you wouldnt be insisting on her not talking to her "friend". i dont buy the only friends now thing, too late for that! we all know this but this might be what she is trying to convince her self of just so she dosnt have to let go of him.
When ever you get angry (and dont understand her feelings) she then focuses on the past hurt and the "reason" the om is the om to begin with! this pushes her away from you and to him. It creates that "need" for him. It only makes things worse and reiterates to her that you will never understand her like he does and there fore what she is trying to do by working out this marriage is impossible and she is stuck in a rut.
I know to you this makes no sense, but this is whats going on when you get upset with her and are not "understanding" of her feelings. The more you get angry and yell at her to not talk to the om the more she is going to feel she needs him. You are not being her friend when you do this. Do you think her girlfriends would get angry and yelll at her for talking to om, or would they empathize with how she is feeling and what she is going through? I agree, we all agree she needs to stop talking to the om however she needs to realize that on her own, as long as she is fought with regarding the matter she will be in a defense mode and there fore wont be in a place to think clearly about the situation with out the pressure of being told what she needs to do. I ended up sneaking ot talk to the OM, when my H backed off and didnt know I was talking to him and quit yelling at me about it we began to be friends there was no more fighting about it or defensiveness about it and I was able to think clearly and come to the point on my own to "make MY decision" if you be suportive of her she can then feel closer to you and not feel she needs to be comforted by him because of you being upset with her about her wanting to talk to him. do you get it???
keep in mind I do hear you and understand where you are comming from and now its your place to be told you must do the "impossible" to save this marriage. I explained her feelings and what situations you two end up in are doing to her. It keeps her in constant turmoil with her emotions.