Accommodations

My wife and I have been together for 9 years, married and living together for 1-1/2 years. Last week she needed to visit her daughter in another city. She made living arrangements in the house of a single guy about our age, the father of a friend of hers who she has heard a lot about, but only met 1 time. She did not tell me about the arrangements, and has stayed in hotels previously. I found out when I overheard her telling her daughter about it and the fact that she planned to take him out for a few beers. When I objected, she became very defensive, insisted that there was nothing wrong with it and would save money. She did not change her plans.

I am very disturbed about this. She knows it, but insists that its my problem.

Any opinions about this?