I've never heard of that happening, on any Unix, Linux, or Mac system. What programs, plugins, enhancements, or other alterations might she be running? Any recent crashes or resets, or other odd behavior? I'm hesitant to say this is a virus, but malware can't yet be ruled out either.
This is one of the weirdest things I've ever seen on a Mac. I was helping my mother-in-law with her computer because she said that all her settings has disappeared when she put her machine to sleep. When I logged in I could see that there was a brand new Library folder in her user directory, as well as a new folder named "[8764" which appeared to contain her old library files. I renamed the new Library to Old_Library and renamed the mystery directory to Library, then rebooted. When the machine finished booting here's what I found"
1. Another brand new Library directory (as well as the Old_Library directory)
2. A directory inside the new Library named "[8764" that contained the original Library contents
I was able to move some files into the newly created Library to restore email, browser and chat settings.
This is one of the strangest things I have ever seen in 15+ years of using a Mac. Anyone have any ideas what's going on here?