To be ungrateful to one's husband. And disbelief is of (different grades) lesser (or greater) degrees.

Narrated Ibn 'Abbas:

The Prophet (ﷺ) said: "I was shown the Hell-fire and that the majority of its dwellers were women who were ungrateful." It was asked, "Do they disbelieve in Allah?" (or are they ungrateful to Allah?) He replied, "They are ungrateful to their husbands and are ungrateful for the favors and the good (charitable deeds) done to them. If you have always been good (benevolent) to one of them and then she sees something in you (not of her liking), she will say, 'I have never received any good from you."