In order to understand this, you have to think like a Borderline. You’ll also need to understand a little bit about your photography career and about what it means psychologically to a model and to yourself. That’s not going to be easy- but if you are ready to consider it, you’ll begin to understand that this photographer/model relationship was a set-up for falsehood from the start-that is, if both people could not separate their identities from the photo fantasies. When you do photography for a living (the work of the magician,) when you deal with fantasy, you will have trouble keeping it from seeping into your personal life unless you understand the pitfalls.  :)ealing with things above the surface can keep you afloat, but what’s hidden underneath has to be dealt with in order to live an authentic life.
Borderline can be easily mistaken for Narcissism and Narcissism can easily be mistaken for Borderline. You have to look deep within to see the difference and find the reward for both. Follow the reward.
Models get allot of attention for their physical appearance. Their beauty must be noticed in order to feel a sense of esteem. (Psychologists call this somatic narcissism.) Somatics place great emphasis on their bodies and face and generally have difficulties when they age, i.e.; their reward system fails. Many somatics fall into depression and begin self destructive “acting out” behaviors. Caution: we are entering the realm of cluster B personality disorders.
Many older Borderlines are failed narcissists. They began life with a concept of grandiosity and then painfully realized that most of their life was an attempt to singlehandedly fix an aging façade. Failing that, they surrounded themselves with sycophants who were human repositories of past glory. Failing to find sycophants, they tried to find strong personalities that supported their idea of their own beauty (their idea of reward.) But I’m getting ahead of myself. I have a feeling that your girlfriend is still young.
Without someone to look at her, she has no payoff. She has to find people that will give her attention-(that is her reward.) The best people are photographers. Photographers are magicians. Photographers give her something that’s more valuable than reality; they give her a record of fantasy, a photograph. They support the Narcissism. Photographers also NEED models to exist. It’s a binary reward system.
Photographers need models, models need photographers. Narcissism is about attention and reward. Borderline is all about attachment and reward. Borderlines are cunning purveyors of who is best suited for attachment. Their idea of who this desired person is- can be summed up by their reward system. How rewarding are you?
Somatics need to be told how great they look. They not only want to be photographed, they need to be photographed. It is their proof to themselves to quiet that gnawing grandiosity gap in their mind. The grandiosity gap is the gap between how great they think they are (really great! =fantasy) and how they really are (average, common, aging, a perishable good =reality.) Because of this grandiose gap, they must get some sense that they exist and are rewarded. That’s where you come in. You have power. You give life to her false self. Why would she want to let that go?
You can give her what she wants-(very rewarding to her idea of her persona) and you can also take it away (withdrawing, punishing and cruel) There is a reason that you photograph- it is your existence and proof of existence to others. She knows this- it’s how you were brought together. She also knows that you photograph others, so attention seeking and acting out behaviors are also a desire to obliterate the competition and keep you focused (no pun intended) on her. Anyone else who gets your attention was and is envied in a “transformation of aggression” and put down by her- that's why she broke contact to tell you of gossip. (Pathological envy is the hallmark of malignant narcissism.)
Borderline is a series of “acting out” behaviors, while Narcissism is attention seeking behavior. From a quick glance, they look the same- but Narcissism is the fear that “I don’t exist,” unless I do this (fill in the blank.) Borderline is the fear that “I won’t exist without you to exist for me.”
So, which do you think it is?  :)o you think it's I don't exist unless I am told I am beautiful? Or... .Do you think it's I dont exist unless I am beautiful enough to have AG70 photograph me, subsume me and make me his own vision? Both have insecurities that hide behind a false mask to become someone else. Both utilize a personality concept- but one works toward an isolated identity while the other is fused.