This is a tough one- I struggle with it myself. I had put it behind me after about a year, but Dday#2 put me right back at square one.
The only contribution I can make is that you have to decide when keeping tabs on her changes from a healthy self-protection measure to a self-harm measure, an attempt at self-punishment caused by the unhealthy responses to trauma that we all have had to deal with.
Every one of us has had our ego crushed, and there's not a person in the world who can make us truly BELIEVE that we're not somehow deserving, on some level, of fault, whether from contributing to the A or how we handle R. It's ridiculous and wrong for us to blame the person in the mirror for the A, but at some point we all do it, and without a healthy ego, how the hell do you defend yourself from blame even when you know, ostensibly, that the fault isn't yours to own?
At that point, her presence in your life becomes partially your choice and responsibility, not just your fWH's. I'm too close to dDay#2, myself to start thinking about letting go, but you have to identify why you're following her, what you can do to achieve the level of security necessary to trust your fWH enough to let go of the need to follow her, and finally, if necessary, you need to talk to a professional if you are past the point where keeping tabs on her is helping you, and yet you still can't stop.
For me, after 6 months I only looked at the OM's footprint online maybe once a week or so. After a year, I stopped except for maybe once every 2-3 months, and afterwards, at the end, I recognized that I was hurting myself by looking.
me- 39, American (BS)
her- 45, South American (WS)
1 child (my stepson)
EA discovered 3/10
D-day (PA discovered) 8/11
D-day II, April 8, 2013 (while overseas w/family)
Attempting R, despite relapse.