She told a lie against her husband; how can she set things straight?
Question

                I have a relative who went back to her father’s house two days after her wedding and told him that the man whom she had married did not pray and that he had said to her obscene words that no sane man would say. She asked her father to ask him for a divorce. Her mahr was 40,000 riyals, but after matters got very complicated and the husband delayed producing the divorce papers, they agreed to give back 30,000 riyals of the mahr. 

The first question is: the woman is asking whether there is any sin on her for taking this ten thousand? She wants to give it back to him so that she can have a clear conscience, but she cannot; can she donate it? 

The second question is: the woman says that she told her father about some things that the husband said and some things that he did to her, and she was telling the truth in that, but she also told her father some things that the husband did not do or say. Is this a serious lie (buhtaan) and how can she ask for his forgiveness, seeing that she cannot go to him and does not know where he is?.
Praise be to Allah.
      Firstly:  The basic principle is that if a woman is 
      divorced after the marriage has been consummated, she is entitled to keep 
      the mahr in full. If the husband did not divorce her until after the mahr 
      was returned to him, this is khula’, which is permissible in return for 
      the mahr, or more or less than that. 

    Based on this, your relative does not have to return the ten 
    thousand to her ex-husband, so long as they agreed that she can keep it. 

    Secondly: If the woman attributed words or deeds to her 
    husband of which he was innocent, then this is a serious lie and is haraam. 
    What she has to do is to repent to Allaah and pray for her husband and for 
    forgiveness for him. She does not have to tell him about that or ask for his 
    forgiveness. The same applies to anyone who backbites or tells lies about 
    another person; it is not a condition of repentance that he should tell him 
    about that, because of the enmity and hatred that that may lead to. 

    Ibn al-Qayyim (may Allaah have mercy on him) said in 
    al-Waabil al-Sayyib, p. 219: 
Chapter 56: What a 
    person who has gossiped about his Muslim brother should say: 

    It is narrated from the Prophet  (peace and blessings of 
    Allaah be upon him) that the expiation for backbiting is to pray for 
    forgiveness for the one concerning whom you gossiped. You should say: O 
    Allaah, forgive us and him. This was narrated by al-Bayhaqi in al-Da’waat 
    al-Kabeer, but he said there is some weakness in its isnaad. 
There are two scholarly 
    opinions concerning this issue, both of which were narrated from Imam Ahmad. 
    The issue is: in repenting from backbiting is it sufficient to pray for 
    forgiveness for the one about whom you gossiped, or must you also tell him 
    and ask for his forgiveness? 

    The correct view is that there is no need to tell him, rather 
    it is sufficient to pray for forgiveness and to speak of his good points in 
    the places where you gossiped about him. This is the view favoured by Shaykh 
    al-Islam Ibn Taymiyah and others. Those who say that it is essential to tell 
    him regarded backbiting as being like financial rights, but the difference 
    between them is obvious. In the case of financial rights, the person who is 
    wronged benefits from the restoration of his rights; if he wishes he may 
    keep it and if he wishes he may give it in charity. But in the case of 
    backbiting, that is not possible and the only thing that results from 
    telling him is the opposite of what the Lawgiver seeks, for it will upset 
    him and hurt his feelings if he hears what was said about him, and it may 
    stir up enmity that can never be assuaged, and there is no point in that. So 
    the wise Lawgiver would never permit or allow it, let alone enjoin it or 
    command it. The aim of sharee’ah is to reduce and eliminate evil, not stir 
    it up and make it worse. And Allaah knows best. 

    Al-Safaareeni said in Sharh Manzoomah al-Adaab, 
    2/577. 

    Ibn ‘Abd al-Barr says in his book Bahjat al-Majaalis: 
    Hudhayfah (may Allaah be pleased with him) said: The expiation of one who 
    has gossiped is to pray for forgiveness (for that person). ‘Abd-Allaah ibn 
    al-Mubaarak said: The way to repent from backbiting is to pray for 
    forgiveness for the one about whom you gossiped. 

    It says in al-Adaab al-Kubra something similar to what 
    Ibn al-Mubaarak said, and this was the view favoured by Shaykh Taqiy al-Deen 
    and by Ibn al-Salaah al-Shaafa’i in his fatwas. 
Shaykh al-Islam (may 
    Allaah be pleased with him) said, after mentioning the two reports 
    concerning this matter: every aspersion against a person’s honour, whether 
    it is truthful or is a lie, comes under the heading of qadhaf (slander), 
    because qadhaf may be true, in which case it is gheebah (backbiting), or it 
    may be false, in which case it is buhtaan (lying). Our companions favoured 
    the view that the victim should not be told, rather du’aa’ should be offered 
    for him, because telling him would cause more hurt and annoyance, and if a 
    person is harmed by knowing what has been said about him, that causes more 
    harm than if he does not know. Telling him leads to these two evils and 
    there is a third evil – even if it is true – which is the destruction of any 
    friendship that may have existed between them, or the renewal of enmity and 
    hatred. Allaah has enjoined us to unite and not to divide. This evil may be 
    worse in some cases than in others. 

    End quote. 
Those scholars who said 
    that it is essential to seek the forgiveness of the one who has been wronged 
    in this matter exempted the backbiter from having to do that if the victim 
    is dead or absent. In that case it is sufficient to pray for forgiveness for 
    him, make du’aa’ for him and do a lot of good deeds. 

    See al-Adhkaar by al-Nawawi, p. 308 

    See also question no. 6308 and 
    23328. 

    And Allaah knows best.