How can a woman deal with her feelings of unhappiness and lack of acceptance towards her righteous and moral husband, despite having performed Istikhara before marriage, and should she continue in this marriage or not?

First: Allah's blessings are many and immense, and humans cannot enumerate them. So how can they give thanks for them? Therefore, Allah Almighty described humanity as unjust and ignorant after stating the immensity of His blessings. Look at the state of one who has lost blessings to realize their greatness, as the Prophet, peace and blessings be upon him, advised.

Second: Pre-marital acquaintances are often unlawful and full of violations, and they do not reveal the full truth of both parties. Love before marriage is based on outward appearances, unlike love after marriage which arises from companionship, affection, and mercy that Allah places between spouses.

Third: Since you have sought guidance from Allah (through Istikhara) and He has blessed you with a committed husband whom you find no fault with in character or religion, this is one of the greatest reasons for your success. You must be content with what Allah has decreed, and remember that Allah has chosen what is best for you. Beware of seeking a divorce without a valid شرعي (Shar'i) reason, as that deprives one of the scent of Paradise.