Wa alaykum salam wa rahmatuLlahi wa barakatuHu,
If a spouse would apostate before the consummation of the marriage, then the separation between them is effectuated immediately. Mawardi mentioned that this is a point of scholarly consensus. (Mughni al-Muhtaj 4:319; Tuhfat al-Muhtaj 7:328)
And Allah knows best.
Answered by Shaykh Yaqub Abdurrahman