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 (ﷺ) is His Slave and Messenger.
If the wife returns to Islam before the completion of her waiting period, then she has returned to your marriage, and the divorce issued during her apostasy is counted.
Shaykh Zakariyya al-Ansaari
stated in Asna al-Mataalib:
“If he divorces her while in apostasy, the divorce is suspended. If Islam then brings them both together again during the waiting period, we determine that the divorce took effect; otherwise, it does not.” [End quote.]
Accordingly, if you have not already issued two divorces before this, there is no impediment to taking her back after her return to Islam. The divorce you issued during her apostasy is counted as a valid divorce, and there is no need to renew the marriage contract.
Allah Knows best.