Is what I told my wife, who suffers from intrusive thoughts of insulting God to herself, correct—that she bears no sin as long as she does not utter the insult, and that she should seek forgiveness and not surrender to the wiles of Satan? And what additional advice is there for her?

The esteemed questioner is correct in what he told his wife. We ask Allah to heal his wife, open her heart, guide her to rectitude, and protect her from the evil of Satan and his polytheism. Let him add to what he told her that she will be rewarded, Allah willing, for her struggle against Satan's whispers and the hardship she experiences from it, and for her frequent seeking of forgiveness.