Is a wife who disagreed with her husband and uttered negative words towards him, then they reconciled before his death, considered among those who are ungrateful to their companion?

If you fell short in your duties towards your husband and he forgave you before his death, then there is nothing held against you. If you fear any lingering consequence, then increase your seeking of forgiveness and supplication for him, and strive in righteous deeds, especially charity, for the Prophet, peace and blessings be upon him, said: "O company of women, give in charity and increase your seeking of forgiveness, for I have seen you as the majority of the inhabitants of Hell." And charity is one of the repellents of punishment.