Just found this:
As urine remains in the bowl, it does go through chemical changes
producing ammonia among other things. Several years ago, one of my
cats always wanted to lick the kitchen and bath floor after it had
been cleaned.
At the time I was cleaning with an ammonia based product. The cats
vet suggested the desire to lick an ammoniated surface may have
something to do with a craving caused by a lack of something in the
cat's diet.
It turned out there was. I had been preparing my own cat food rather
than using commercially prepared diets. After further investigation,
the vet told me the cat was lacking a substance called "taurine,"
which is added to commercial preparations but is often lacking in home
prepared foods.
Might be worth your friend checking out the contents of her cats food!
