A couple of more that come to my mind:
There's a couple of occasions where D.W. slips into Arthur's bed, either because she was scared for him, or felt bad for him, those are usually really sweet little scenes.
Also, from "Arthur's Lucky Pencil", D.W. stops Arthur from stepping on the pencil. "You could have tripped and DIED! I saved your life!" From D.W.'s perspective, I'm sure seeing Arthur trip on a pencil would probably seem like a big deal to her, so I think it's really funny and sweet that she "saved his life".