How we cite our quotes: (Chapter.Paragraph)
Quote #1
Marilla looked at Anne and softened at sight of the child's pale face with its look of mute misery—the misery of a helpless little creature who finds itself once more caught in the trap from which it had escaped. Marilla felt an uncomfortable conviction that, if she denied the appeal of that look, it would haunt her to her dying day. Moreover, she did not fancy Mrs. Blewett. To hand a sensitive, "high-strung" child over to such a woman! No, she could not take the responsibility of doing that! (6.20)
Besides her religious beliefs, Marilla has another set of morals that some of the people around her, like Mrs. Spencer, don't seem to have. Marilla could choose to believe it isn't her responsibility where Anne ends up, since Anne came to her by accident in the first place. But Marilla sees Anne as a real person in need of help, and that's where her sense of duty kicks in.
Quote #2
"And, since you seem to want her, I suppose I'm willing—or have to be. I've been thinking over the idea until I've got kind of used to it. It seems like a sort of duty. I've never brought up a child, especially a girl, and I dare say I'll make a terrible mess of it." (6.32)
Marilla's reached a point where she doesn't see a choice. She has to keep Anne. Note that she doesn't use the word "like" at all when describing how she feels about Anne. Marilla's all duty and responsibility at this point.
Quote #3
Marilla was as fond of morals as the Duchess of Wonderland, and was firmly convinced that one should be tacked on to every remark made to a child who was being brought up. (8.42)
With no idea of how to teach a child, Marilla winds up parroting morals, as if that's the best way for a child to learn.