Is it permissible for a married sister to tell her unmarried sister details of her marital relationship and intercourse with her husband?

Matters that transpire between spouses, such as their private enjoyment of each other, are a trust that must not be divulged. This is based on the Prophet's (peace and blessings be upon him) saying: "Indeed, among the worst people in station before Allah on the Day of Resurrection is a man who goes to his wife, and she goes to him, then he divulges her secret." This warning encompasses both men and women. It is not permissible for a woman to tell her sister or anyone else about the matters of enjoyment that will occur between her and her husband.