Just an opinion from from real life experience and advice from a friend. My ex-wife ( not ex at the time) was talking to a man I didn't know. I found some cards etc. were exchanged and in my gut, I felt like something was wrong but, was not sure and I wanted to trust her. I confided in a woman I worked with and she said " if this man was just a friend, tell her to introduce you to him and maybe we could get to know each other" Well, after I told her this, she confessed that it was an affair. I think that if you want a good relationship, you should at least know of all the friends the other has, you might not become friends with them but, you will at least know if they have something going on or not. It is very difficult to hide feelings in person. Just my 2 cents. And I do believe it is very difficult for men to be just friends with a woman......the men almost always want more then just friendship