Facebook Friends

This week my wife is away for a few days so that she can go to the funeral of her ex-stepdad on Thursday. I'm at home with my son because he has school to go to.
Last night we phoned my wife to speak to her so that my son could tell her what he'd been up to at school and also stay goodnight before he went to bed.
When he came off the phone I spent a few minutes chatting with my wife going over what we'd been doing and what we had to do before she comes back Thursday evening.
While we were chatting, completely out of the blue she mentioned that she had been on Facebook and had searched for her ex-fiancee, had found him, sent a friend request, which he had accepted and had chatted to him online.
Later on yesterday evening I popped onto Facebook and had a nose at her friends list and low and behold he was showing as a friend.
Now we've been together for nearly 17 years, she had split from him a year or two before we met. Unfortunately he came back into her life because of a flat that they'd owned together and had handed to the mortgage people who had sold it at a loss at the time then come chasing them for the remainder of the mortgage money years later.
Now the relationship was very rocky and he didn't treat her well, in fact her mum actually hit him and gave him a blackeye after one incident.
Over the years the wife has brought up various things that they did, she has evening mentioned his mum and how good their relationship was compared to the one that she has with my mum.

When I first got together with my wife I made the mistake of letting slip that I liked Marion, a work colleague, and would have loved it if our relationship could have gone further. There was no way that it could have due to us both being with other people. However, when we moved to the area we now live I still had the odd contact with Marion. Things came to a head at one point when after talking with Marion, the wife gave me an ultimatum which was to split up with her or to stop having contact with "the Bitch" as she called Marion.
Being deeply in love with my wife I allowed my friendship to fade.

Now 15 years later here I am finding out that my wife has now instigated contact with her ex. I can honestly say that I don't understand why she has done it. What I am beginning to understand is why you see reports in newspapers about relationships and marriages that break up because of what people do on Facebook.
To be honest if it wasn't for the fact that I don't want to do something rash I'd be almost tempted to turn around and tell her about transitioning as a result of what she's just done. Just get it done and be shot of her two-faced nature once and for all.

Or perhaps I should simply see if I can find Marion on Facebook and renew my friendship.