1. Yes it is perfectly possible and indeed probable that she sees this work as exactly that... work. That is all it is, a means of earning money. The real problem here is that you are mistaking the sacredness of a relationship with simple natural nudity. The two are, in my opinion, very different. I am male and would have no issues whatsoever with my wife/girlfriend getting undressed and being photgraphed, painted, filmed if that was her desire and her career choice made her happy. Ideally you should feel secure enough in her for this not to be an issue for you both.
2.If she carries on she is simply stating her individuality and sense of self, it in no way implies that she doesn't love you, possibly quite the contrary as if she gave in and stopped she would likely become resentful of being controlled. If she knows this to be true of herself she could in fact be doing you a huge favour in asking you to re-evaluate how you feel about, rather than condemning the realtionship to death at a later date out of resentment.
3.Physical intimacy and nudity are two different things, in my opinion and obviously in hers, I'm not sure it will be easy for her to understand as she clearly lays very strong claim, quite rightly, to her body. She may share it with you, but it remains hers to decide about... and if she doesn't feel that her work and her realtionship should be judged on the same plane then I think you will struggle to make her see otherwise.