So exactly how do you make a friend in an art class? My answer is to ask open ended questions. Questions that cannot be answered with just a yes or no answer, but require more of an explanation, so you might learn more about the person.
Here is a list:
To ask at the beginning of the class or while waiting for the teacher to begin. How did you find this art class? What other kinds of art do you do? Are you from this area? What other art classes have you taken? Where did you get that brush?
To ask while doing the project. How did you get that technique? With an exclamation first, Wow, I love the color you used for the sky, where did you find that color? Amazing! How did you learn to draw like that? Awesome! Have you been painting for a long time?
At break time. If you are stumped for questions to ask, just look around and ask questions about the environment. Do you know where the coffee machine is? Did you think the man across the table is wearing a wig? Why do you think the teacher dresses like that? Or if all else fails, give a small compliment and then ask a question. I love you shoes, where did you find those?
Nearing the end of class you could ask things like, What do you think about taking another class from this teacher? Are you going to be able to continue this drawing/journaling/painting or whatever process on your own at home? Then you could throw in, maybe we could form a group to continue painting?
It's very scary to try to make new friends at any age, once you leave kindergarten. I think its because no one likes to be rejected. However, we can't take rejection personally. Compare it to something else like fishing. You bait the hook and you drop it in the water and wait for a bite. Then if you get a bite you have to pull the fish out of the water and see if you want to take it home. Maybe this isn't the best analogy, because you are not going to eat your new friend for dinner. But, I can't think of a better analogy right now. So just be open to trying to make new friends in art classes. Let me know how it goes.