Please sit your woman down and have a heart to heart serious discussion with her concerning the extent your so-call friend has gone with her. Do make her understand that the discussion is very serious and her co-operation is highly needed. This is to enable you access the situation properly before taking any decision on the issue. But if she still refuses to give you full details, it then means something is already happening between she and the guy. I wish u success in your discussion with your girl. Thank you!