Is there a problem with my girl going out with a guy friend?

The girl that I've been dating for the past 3 month is going out with a guy friend tonight. She told me this the other night when I told her that I didn't know if I was to be working tonight or not. She told me that her friend Danny, whose wife died a few months back is having issues and wanted my girl to spend time with him tonight. Dinner, Movie, A few drinks after. When I objected to this (I've never net him and didn't know he existed), she told me that it was strictly platonic and that they are just friends. The thing that I'm getting is, this has happened to me before in the past and it turned out they were more 'friends with benefits' than what I was told. She's now mad at me for objecting to her friend who is going through a hard time. We're both in our early 40's and I'm too old to play these type of games. I considering dumping her over this issue, even though in everything else, we are a perfect match.