How would you feel if your girlfriend does nude modelling?

I wouldn't have her as my girlfriend.

I had to take college art as a prerequisite for another class.  It was actually one of the better deals of college and I receive compliments on my quick mechanical drawings to this day.  Much to my surprise we had nude female models. It was interesting how the males of the class focused in on private parts, I was a form and hands guy. 

I ran into close association with one model for a common event outside of college and she (of course) treated me weird. I wanted to speak to her and tell her to regard me just as a fellow student in a different class, never did, never saw her again.  

Most of the models left the area upon class break, one didn't and took break with the students. I liked her more than the others but never interacted with her different than the other female students in the class.  

How would I act if it were my girlfriend?  I would support her decision.  And perhaps tell her to take break with the students if she were comfortable with it?

They are using her just like a paid hooker.  They get off on messing with her.  You can start by going to the County Attorney and letting them know.  They will probably look into it and could file criminal charges.  Maybe your girl friend knows she is being used and likes it.

Two of mine did.

Honestly and obviously you and her relationship is important, so you might bring up these matters again, but it’s her job, and your feelings are also as important. If it bothers you and she doesn’t change and continues/loves her job, maybe you might want to find a classy woman who doesn’t show her body to others let alone have others draw her nude.

This is something you need to decide and have a talk before anything else.

I never experienced this as I’m not in a relationship to know, but both parties need understanding of each other’s feelings (a lot of ancient writings talk about this, and there are advice found in books or elsewhere about this).

100% fine by me.  If she's satisfied, nothing else matters.  It's her life, isn't it?  I don't have any ownership deed for her, do I?  

The pay is excellent,  the work isn't strenuous and there's a teacher there in the life modeling class. 

It's not your life.  It's hers. If you can't stop your hangups then find a different girlfriend.  She's an adult. 

Have you ever done a life drawing class?  To get an insight - try one.  There maybe those that go because of the perv aspect but they’ll be obvious and probably not good artists.  Hopefully the person hosting the class has your friends safety as priority.  It is usually a safe space for all those concerned.  And don’t forget drawing and painting the human form is a time honoured practice in art.  

Sounds like you might have a girlfriend that is destined to appear in one of those gross x-rated pornographic movies.

I'd be uncomfortable, too.