Ladies, is it normal for my girl friend to not be jealous with my work

My girl friend is a very open person with a bisexual attraction. We've been together for almost two years and we have a wonderful relationship with each other. I'm trying to understand the mind of a female because my girl friend is very much ok with the work I do for a living.

I model for sensual nude art for my profession, in which I pose with other female models in the nude. I model for a number of professional European artists who do paintings and sculptors. The art work is very sensual within it's nature and the purpose of the art is to express the essence of sexuality between a man and woman and also between two women. Sometimes I'll pose with just one female model for an art session and other art sessions I'll pose with two or three female models, depending on what the artists intentions are. Now I don't mean to get too explicit, though I just want to say that the artists believe that in order to make the art look as real as possible, to bring the art to life, and to bring to the art it's true meaning and message, I have to actually penetrate ... though we don't continue on with the act (and yes it does take a TREMENDOUS amount of patience and self control to keep the work professional). So basically the artists believe that penetration is very necessary for artistic purposes.

Like I said earlier, my girl friend is very much ok with what I do for a living. Many times she even likes to visit the art studio and watch me model in art sessions. I asked her if she gets jealous with watching me modeling in passionate sensual poses with other women. She tells me it doesn't bother her at all, but instead it turns her on A LOT to watch me model in the type of art I work in.

I'm just very surprised that a girl can be like this, lol! I'm just VERY surprised about this and not sure what to make out of it. What's going on here? lol

I'm not complaining here, just to let you all know. I'm just wanting to know how a girl can be like this, that's all. I'm just trying to understand the mind of a female. Is it even possible for a man to understand the mind of a female?