Is a divorced woman's refusal to tell her mother about her ex-husband's request for her on the wedding night considered backbiting (gheebah) or divulging a secret, and should she fear divine punishment for it?

It is forbidden to disclose the secrets of marital intimacy. What is prohibited is mentioning the details of what occurs in terms of words or actions. As for merely mentioning intercourse, it is disliked if there is no benefit or need for it, but if there is a need for it, then there is no dislike. The general statements mentioned do not fall under the prohibited disclosure of secrets, but they may constitute forbidden backbiting, which is speaking ill of a person in their absence, and repentance from it is obligatory. It is not appropriate to speak with one's mother about such a matter, which is usually considered shameful.