It was painful to watch through this but I got a good idea of what the writer and director were getting at. It is a fascinating subject. While studying the issue of class in relationships, the main theme as I saw it was about dis-empowerment. Spoilers to follow.
Psychologists have demonstrated that rape is about power. Not sex. A man feeling powerless dominating another. It is not about lust. The working class, dark skinned protagonist does not have much in his life in French society besides brandishing machismo-ism Similarly, promiscuity, in particular in the female, comes from a deep seated feeling of not being loved, and low self esteem. At first glance this would not seem to apply to the female protagonist. But we don't know anything about her family life, where all this is rooted.
She does abandon a lackluster man who is eager to please her at the Beijing university, with whom she appearers to have been living, and runs after a French man to Paris. A man who had been in Beijing she'd met at the university and had what sounds like a brief consuming relationship.
Later, being raped and then really repeatedly raped countless times by her machismo, working class pursuer,( for no one with any knowledge of female sexuality would say she is getting satisfaction from that kind of violent banging) is a clear sign of her depression. It is the cuddling afterward that gives her true satisfaction. It is not about sex, it is about a need to feel close, and some deep seated insecurity.
Running parallel to this is the issue of how we don't want what is easy, run after what seems unattainable,and reject those who plead with us obsequiously. It made me wince to see the ex lovers being rejected in such cruel ways dramatized enough times for emphasis in the script.
It's easy to say Flower should just return to the cool job she has in Beijing that many would die for. Hopefully she will. Hopefully she can find her inner power and move forward knowing that she will find in the course of her interesting career an intellectual, strong but gentle man she needs for a good partnership. She needs to read "The Rules" and "You Lost Him at Hello" in the meanwhile. lol
As for the male protagonist left behind in a working class life with no clear options to rise above, one can only hope for some chance, some change in him, to be a better man, some counseling for abusing women, return to his wife and baby. At least he is shown to have a warm family hearth to come home to, but an environment non the less which has been responsible for him feeling such a need to show power by being abusive to women.
It might all seem like sex, but at heart it's all just an acting out of a desperation for love and self esteem, and feeling powerless to achieve one's dreams hampered by social divisions.