The Guardian obituary raises further complications. The first song mentioned is not The Partisan, but another (subsequently more famous; Le chant des partisans or later, apparently, Le Chant de la Libération) and which is also referred to by Marc Gaffié (see link above). As Gaffié states, "Bernard" wrote the French words for La Complainte du Partisan (the song later recorded by Leonard Cohen and others); this is confirmed in the Guardian piece, though it doesn't say specifically that Marly wrote the music.

I can see how "Purple Foxx" might have become confused by all that; the song titles are very similar, and the obit isn't as specific as it might be. Neither does Marc Gaffié mention any involvement of Anna Marly's in the song usually credited to Joseph Kessel and Maurice Druon; which Patrick O'Connor states is a translation of a song originally written by Marly in Russian. I'm getting confused, too.