My wife has a notification on Facebook when somebody unfriends her and it tells her who an when. How do I get?

[Monroe71202]

[tcwnn]

Good question, because Facebook doesn't give out that information.
Sounds to me like an app that you have to "like". The app also gains access to your profile, friends list and other info.
If you see an app, telling you you can see who unfriended you, don't go near it. It's spam.
Tell your wife to block any similar apps if she has them

[Jan409]

There's no such thing as an app that tells you who has unfriended you
if she's got this, then it is spam, and certainly won't work, but it may interfere with her f/b account

[isashach]

Don't listen to all those idiots who tell you that you need an app or that this doesn't exist.

This does exist, and I have been using it for years. Its called Unfriend Finder, and it's simply a user script that you can install directly in Chrome, or using GreaseMonkey in Firefox.