Her duplicity hurts me more than all; till the very last, if I reasoned with her, she declared herself as much attached to me as ever, and laughed at my fears. I am ashamed to think how long I bore with it; but if ever man had reason to believe himself loved, I was that man. I cannot understand even now what she would be at, for there could be no need of my being played off to make her secure of Tilney. We parted at last by mutual consent — happy for me had we never met! I can never expect to know such another woman! (NA, 23)

James’ writes to Catherine of how Isabella’s duplicity gave him pain and his shame at being fooled by her manipulations for too long but although Mr. Rushworth could say something of the same nature with better cause yet he never does. After all by the play Maria is not in the least obliging or at all attentive while Isabella continued to play a part to James. As you point out it seems clear Mr. Rushworth understood Maria was cold and inattentive to him and too warm and attentive to Mr. Crawford. I think his indecisiveness and willingness to let others, such as Mary (17), sooth over his jealousies are reasons he did not confront Maria but cannot be an excuse. Despite how Maria treats him I think Mr. Rushworth is unwilling to risk a breach by confrontation and risking her choosing Henry over him. However I am not exactly sure what Mr. Rushworth is so mindlessly attached to. Maria is handsome but she is cold towards to him and it hardly seems possible any regard she initially showed in order to secure him was so extravagant it gentles her present behavior. I feel Mr. Rushworth has been ill-used by Maria but it is difficult to feel too sorry for him since he is well aware of her disloyalty. (:D)