Facebook is just a tool. A #2 phillips screwdriver can tighten a wobbly table leg or pierce a kidney with equal ease. There is no difference between them. It comes down to the intent and actions of the user.
The new situation will suck for awhile... that's a given. Once the bond of trust has been broken in this way, she's gone. Period. Been there, done that, got half a t-shirt. The trick is to find an outlet for the inevitable bad energies you'll be experiencing.
While I don't wish anything bad upon my delightful ex-wife (not today, anyway) I wouldn't be a bit upset to learn of her having a stroke or falling off of something tall. She's just not worth the energy. She's doing her thing, I'm doing mine and never the twain shall meet.