Is spreading news about forbidden relationships or suspicions of adultery, whether this news comes from the girl's own confession or is merely rumors circulated by people, considered a slander against chaste, believing women? Does this lead to sin and unforgiveness? And does confronting and advising the girl accused of such actions fall under the category of slander?

A Muslim is commanded to turn away from unfruitful words and deeds. Their speech is part of their actions, and it is forbidden for them to delve into the honor of Muslims. You are sinful for informing your friend about a forbidden relationship based on rumors; this is forbidden backbiting (gheebah), not slander (qadhf). The sin is not removed by the girl's own confession; it would have been more appropriate for you to conceal her secret. There is a warning against narrating everything one hears without verification. Entering Paradise is among the matters of the unseen. It is more appropriate for you to stay away from delving into these matters, and to advise those who do so, or to leave the gathering if the advice is not heeded. You are sinful for confronting the girl and asking her about the truth of her situation, and for saying harsh words to her, as this is uncovering the private matters of Muslims and harming them. You must repent immediately, seek forgiveness, refrain from delving into the honor of Muslims, and ask the girl for her forgiveness.