My initial thoughts are this:

It is not really about who Sophie is...or Mary or Elizabeth... or Jane Doe. It is about who your husband is. Should he eliminate his friends so that you can feel secure? I think not. By the same token... "WHAT" is a friend to him? And, what does the relationship entail? Does he have other friends? If so, does it seem that he handles those relationships any differently? How long have you been married to this man and what age range are the two of you. All of those factors play such a part in the dynamics of this situation. Wondering