What is the response to a woman who casts doubt on the religion and claims that the verse about the number of the People of the Cave is laughable, as though Allah did not know their number?

Mocking the Quran and belittling it is disbelief in Allah. The noble verse discusses the اختلاف (difference of opinion) among people regarding the number of the People of the Cave. Allah Almighty knows their number, and He has stated that some people also know their number, such as His saying, "They will say, 'Three, their dog being the fourth,' and [others] will say, 'Five, their dog being the sixth' — [saying so] in assumption of the unseen; and [yet others] will say, 'Seven, their dog being the eighth.' Say, 'My Lord is most knowing of their number. None knows them except a few.'" Ibn Kathir interpreted that the verse indicates the correctness of the statement that they were seven and their dog was the eighth, and that it is better to refer the knowledge to Allah. Allah has informed us that a few of creation know their number, among them Muhammad (peace be upon him). Ibn Abbas mentioned that he was among the few who knew that, and that they were seven.