yes
Thomas Crapper was given credit for it but it was Sir John Harrington's idea.
Technically, yes. You can grind it up and eat the grounds. But it would be a bad idea because your body can't pull nutrition from it, it might reform and clog your intestines, and your body might absorb a chemical that will harm your body.
If she has that bad of a phobia she can seek help for this. If you are in the area and are friends - maybe clean it for her every so often - what are friends for. How about the cleaner that is placed in the tank and works when it flushes that may relieve some anxiety for her.