To get it out of the way, I never believed that Roger Vadim created BB or vice versa. They were both products of a film era that needed urgently some sexual awakening with the difference that he was a not-so-hot writer-director while she was a force of nature waiting to unleash her power. And boy did she do it!
Almost two decades after "Et Dieu... créa la femme" (1956) and after trying for years to replicate its success with BB stand-ins (Jane Fonda, Annette Stroyberg, Rebecca De Mornay, etc.) Vadim reunited with Bardot for what must have seemed (to them) a terrific idea: BB, the eternal seducer as Don Juan, the seducer par excellence. BB playing a stud? Not on your life! Her part is of a female seducer who thinks she was Don Juan on a previous incarnation. Really.
I think all this Don Juan business is just an excuse to show some hanky panky between Bardot and Birkin since lesbian love scenes were very popular in the early 70s and Vadim gracefully obliged. After all, if he wanted to presume of remaining a cinema transgresseur, showing BB in a lesbian situation is not such a bad idea. However by 1973 Bardot was no longer BB, that half a child, half a woman that conquered the world. Mind you, her charm and personality was still there but her face showed the puffiness and lines of middle age in spite of being shot through filters and special lightning.
Maybe the Don Juan concept could have worked better ten or fifteen years before but, if you are a Bardot follower, you know she did something very similar in Julien Duvivier´s "La femme et le pantin" (1959) filmed in Spain. I say "similar" because the story, although based on a novel by Pierre Louÿs, owes a lot to Prosper Mérimée' s "Carmen", that gypsy dame who plays with men' s emotions, a part that seem designed for BB who was then at the top of her powers as the ultimate seductress. Who is Carmen but a female version of Don Juan?
In short this is a not-so-good-film that must be seen for several reasons. First of all because it marked the end of Bardot' s film career (she did another film in 1973 and that was it), also for the presence of two actors that are also true cinema legends, Maurice Ronet and Robert Hossein (both deserve better). Last but not least, some praise must go to the Eastmancolor cinematography by veteran cameraman Henri Decaë. The rest you can throw away, Vadim et all.