First, I wouldn't play your cards right away......Be a detective and find out concrete info, if you really want to know, before you confront her........Otherwise, you'll get some BS excuse, she'll try and cover everything up and then you're left in the dark with only your wife's word(nothing happened) and your belief(something happened) which will eat at you......play it cool and act like you didn't see it for the time being until you can find out more.......
Theres alot of questions I could ask you that could change the situation, How close you guys are? Do you guys talk about everything? Let me look for a few articles and I'll get back to you