Is there hope for a woman who swore a false oath in court, claiming her husband beat her, knowing that she cannot go back and change her testimony, and that a ghamos oath has no expiation except repentance and the restitution of rights?

The perjurious oath (al-yamin al-ghamūs) is a grave matter and a major sin. It does not lead to eternal damnation in Hell, but it plunges its taker into it. What you have committed by swearing a false oath is a grave evil, especially if it resulted in injustice. Your duty is to repent sincerely and strive to restore the rights to your husband if any harm resulted. You must also recant your false testimony to those who heard it, provided you do not fear harm from doing so. Furthermore, you should increase your supplications for forgiveness, perform righteous deeds, and maintain a good opinion of Allah.