Is the wife entitled to refuse to share her husband's bed because he delays performing Fajr prayer until 6:00 AM?

It is not permissible for a wife to refuse her husband's intimacy except for a valid, sharia-compliant excuse, such as illness and the like, due to what is mentioned in the hadith: "If a man calls his wife to his bed and she refuses to come, the angels curse her until morning."

And also the hadith: "If a man calls his wife for his need, she should come to him even if she is on the oven."

A husband delaying prayer or abandoning congregational prayer does not permit the wife to deny him his rights that are obligatory by Sharia, such as intimacy. Rather, she should admonish him and disapprove of his action with kindness.