All perfect praise be to Allah, The Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad is His slave and Messenger.
We have already highlighted that the bridal gift is the exclusive right of the wife in fatwa 84252. That is the principle.
If your wife had promised to give you back the bridal gift, then the scholars differed in opinion concerning the ruling of fulfilling the promise; in this regard, please refer to fatwa 84051. Some scholars said that if the promised person incurs a loss because of the promise, then it is an obligation to fulfill this promise. Based on this, if your wife led you to incur a loss because of her promise to pay this big amount of money as a bridal gift back to you, then she is obliged to fulfill whatever she had promised you.
Finally, we should point out that if this woman is righteous and you expect that the marital life would last with her, we advise you to take her back. If you take her back during her waiting period from a revocable divorce, then there is no need for a new contract. But if the waiting period has expired, then there must be a new contract and the woman deserves a new bridal gift as well. For more benefit, please refer to fatwa 82541.
We advise that the bridal gift should not be a large sum, because a small bridal gift is one of the reasons for the marriage to be blessed by Allah. ‘Aa’ishah, may Allah be pleased with her, narrated that the Prophet said, “It is from the blessing in a woman that she has an easy bridal gift, an easy proposal [via her guardian], and an easy womb (i.e. she is fertile, bears children without difficulty, and responds to the call of her husband for sexual relations).” [Ahmad]
Allah knows best.