Just keep in mind, the ray of hope isn't for us. Your MLC spouse will be begging for a ray of hope one day (or they'll continue to spiral out of control the rest of their lives). They will get a second chance if we want to accept it. Unfortunately, by that time, most of us will have moved on. Just keep living your life as if she isn't coming back...and one day, out of the blue, when you least expect it, is when they usually try to return. Then it is decision time for you...a very tough decision.
The destruction they cause is on par with a metaphorical nuke and long lasting. And it will still bite you years down the road even if you reconcile. I got stung financially recently from when she returned the first time. She wracked up tons of debt that I had no idea about.
In the end, they destroy themselves. As much pain and loneliness they cause us, it will hit them twice as hard eventually.
One thing that amazes me is the amount of people that seem to be OK with what she's doing. Do we really have that many screwed up, depressed, immoral people living in the world?!? I mean, who "likes" a facebook post from the OM who says he was with my W for the weekend?! Messed up world we live in...