Carmela knew what she was dealing with for a long time. Heres her confession to the priest [season 1 episode 6] after her hole jealousy thing over that phone call from Dr.Melphi:

What's killing me is this is a self-inflicted wound. I pushed for it. I could deal with the goomas. I know I was better than them. Stupid as it sounds I viewed them as a form of masturbation for him. I couldn't give him what he needed all the time. You're a man, father, you know that thirst. I was too busy with the house and kids to quench it. But this psychiatrist, she's not just a gooma. For the first time I feel like he's really cheating and I'm the one who's thirsty. I'm not gonna stay in a marriage that's made of... [at this point the priest said to her divorce is for the weak etc..]

Meadow even got upset at her for putting up with it for so long as you saw in this final episode. This is not just a "Tony being unfaithful" thing. If you ask me it had everything to do with the "Furio leaving to Italy" drama. That struck her like a bolt and made her very moody towards everyone in the family. Notice last episode she was already talking like she didnt care if she saw Meadow ever again after that arguement with her? Even Meadow brought it up to her about this being all about Furio. I was hoping that arguement wouldve continued so that she could really get under her skin.

I sure hope this show doesnt get any cornier by showing Carmela chasing after Furio in Italy. If theres really any suspense in this for me, it is to hear what Dr.Melphi has to say to Tony about all this.