However, since CFC is an abbreviation (which she acknowledges by writing it in upper case), it is not unreasonable to write "CFC's", since the apostrophe replaces the missing "arbon".
Similarly, when abbreviating "telephone" to "phone", it would not be unreasonable to replace the missing letters by an apostrophe, if so preferred.
It would be archaic to do, but that wouldn't make it incorrect.
The English language is an imprecise and ambiguous tool, and we should tolerate personal preferences of style.
David Le Fevre