She didn't simplify it to FSL, she simply translated the French Langue des Francais to the English equivilent, French Sign Language. She didn't use an acronym at all, but rather translated the phrase that the acronym stands for. English and French have different syntaxes. Literally, the translation would be Language Sign of the French. Doesn't make much sense in English, though, due to the differences in syntax between the languages.
