Hey Maven, I know this is a little late, but I wanted to know how things are turning out?
I was wondering if there was anyway you could maybe get a stool, like a collapsible step stool for painting on the easel. Also, would it be financially feasible to purchase a book instead of going to the library? I know art books can be fairly expensive (art history major over here), but if that would enable you to do the assignment with less anxiety from your OCD, that might be worth looking into.
I also agree you should try talking to the professor. An email might be easier than face to face, but it seems like she wants her students to succeed and would like to do what she can to help them. I know it's anxiety-inducing, but it might help you long term.
Good luck!