Hi Julio! He may be right, although Simone de Beauvoir uses 'liberation of women' in the Second Sex in 1949, and part of the context had to be the liberation of France. That was translated into English in 1953. There is also the Algerian NLF, before the Vietnamese NLF. It seems right, though, that its use in the U.S. was encouraged by the Vietnamese use of the term. Feminists likely got it from De Beauvoir initially, though.
Jenny Brown