Seems like that part was brushed up. I'm guessing she wanted part of her arm (and I'm also guessing her face) to be lighter in order to give it a more 'dramatic' look. She probably forgot to blend it properly.
I was wondering if I was the only one to notice that...it almost looks like two different pictures were put together, and one had a slight shadow and the other one had full light on it. I am confused.