Is it ok for a spouse to meet online friends for lunch?

To make this short my wife has been talking to a guy online that she used to know in high school. She has been honest to me about him and has told me that he's in a bad marrage and needs a outlet to vent because he does not want to let their mutual friends to know of their problems. He suggested they should meet for lunch one day and she seems to be ok with meeting up with him for lunch. Personally I do not think its appropriate for a married woman with two kids to meet with other men especially ones in bad marriages. We have had our issues of our own if you look at my posting history you know I dont need more crap to think about. They talk on facebook about their issues but I do not see any flirting between them. He's not a looker at all and overweight so I know shes not attracted to him. But I almost guarantee she would not tell me if she were to meet him because she would not look at it as as her doing anything wrong lunch is just lunch to her. Am I wrong? do I need to loosen up? Or does she need to grow up and consider me and her kids especially after last year?