To bring peace in the family, you should try to make friends with the man she loved her parents. It should be done carefully. To begin to talk separately with mom and dad, alone with her husband. Describe all of the most valuable and good qualities of character of the opposing sides. Explain how you trouble of war. You are caught between two fires, and just can not take someone's side, because all you are very expensive. After this meet me. Better if it will be held on neutral territory - in a cafe in the park, on a picnic. So all parties to the conflict will be on an equal footing. And a public place will not let the conversation turn reconciling the fray.
Monitor the process of negotiations, cropped dangerous topics. You know the weaknesses of loved ones, so try to talk to them are not affected. Be sure ozvuchte as you are happy that everything came together and how you do not have enough of these family gatherings.
After the first meeting, let family time to think. Do not mind about what happened, let them decide what to do next. Most likely, someone will express the wish to continue the dialogue to get to know each other better. Periodic visits to the guests and regular communication by telephone necessarily reconciled the conflicting parties. There are common topics of conversation, and perhaps you dear people still become good friends.