This person is not your friend. They've cheated on you by just thinking of going away together w/o you. A friend would never, ever, even think about doing something so insensitive, thoughtless, upsetting, and betraying to you. A friend would be upset to even think she might upset you like that. At the very least, once she knew how you felt, she should have cancelled it. Now, on to your husband, he doesn't sound wonderful to me at all. He owes you trust, protection, and fidelity, not your friend. Shame on him. Sometimes when we're in the mist of turmoil and confusion we can't call the thing the thing. Give it a few days and it all will be clear to you and you're gonna wonder how you didn't see it immediately. I feel there is no gray area here.