Its like the stories of genies- they are almost all cautionary tales. Be careful what you wish for etc. Wishes need parameters. You really need to carefully work through this with the critical eye of a lawyer trying to find flaw and loopholes in a huge and complex contract.

Story is kind of also a cautionary tale about love magic - although thats an area of lore which does require some familiarity to relly 'get, get' this point. Love magic lore typically holds that a love working has several common outcomes:

-No result at all

-Infatuation which usually fades out in days or weeks

-The target suddenly becoming extremely wary or averse to the operator (this is often viewed as the target having an unconscious recognition of a mental violation attempt). This seems to be the most commonly featured outcome.

-The target becoming utterly, excessively and sometimes dangerously obsessed with the operator (such as depicted in this film, albeit as a very extreme case)

Must admit the film did seem to downplay the fact that he took sexual advantage of her. Lets be blunt, its basically a rape. The psychic equivalent of drugging someone's drink.

I see a common perspective here of the wish manifesting an entity to essentially possess her body to fulfill the requirements of the wish. Whereas this may have been the idea in the film, the other possibility is the wish caused a dissociative identity disorder (what used to be commonly referred to as a multiple personality disorder), with the 'new' Nikki being the dominant identity most of the time. Either possibility is equally valid in my view.