Separation of spouses is something that the Shaytan loves and is keen to make happen.
Muslim (5023) narrated that Jabir said: The Messenger of Allah (blessings and peace of Allah be upon him) said: “Iblis placed his throne on water then he sends out his emissaries, and the closest of them to him in status is the one who causes the most fitnah (trouble). One of them comes and says, ‘I did such and such,’ and he says, ‘You have not done much.’ Then another of them comes and says, ‘I did not leave him alone until I caused division between him and his wife,’ and he draws him close to him and says, ‘How good you are.’”
Al-Nawawi said in Sharh Sahih Muslim:
Regarding the words “and he draws him close to him and says, ‘How good you are’”, he praises him because he is impressed with what he did, and he achieved the goal that he wanted. End quote.
Abu Dawud (2178) narrated that the Prophet (blessings and peace of Allah be upon him) said: “The most hateful of permissible things to Allah is divorce,” The isnad of this hadith is da‘if (weak), but its meaning is sound, as has been explained previously in the answer to question no. 120761 .
If that is the case, then how can a Muslim celebrate the occurrence of something that Allah, may He be exalted, hates and that the Shaytan is pleased with and encourages?
That is in addition to what may happen in such a celebration of evils and objectionable matters, such as free mixing between men and women, wanton display of beauty (tabarruj), temptation (fitnah), music and singing.
Moreover, this celebration is offensive to the husband and closes the door to any possibility of the spouses coming back together, because if the husband finds out that his wife has held a celebration when the khul‘ took place, it is unlikely that he will think of going back to her.
Conclusion: what appears to be the case is that this kind of innovated celebration and unacceptable custom is not allowed. The marriage contract is something sacred, and there are rules and etiquette to be observed when it is to be dissolved. In fact, the husband has rights, even after separation, and it is for this reason that ‘iddah has been prescribed.
If the husband is abusive towards the wife, and she cannot find any way to free herself from his abuse except by means of khul‘, and she manages to do that, then it is sufficient for her to say “Al-hamdu Lillah” and praise Allah, may He be exalted, for having saved her from this abuser, without celebrating and showing excessive joy.
And Allah knows best.