Wa `alaykum As-Salamu wa Rahmatullahi wa Barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
Dear questioner, we would like to thank you for the great confidence you place in us, and we implore Allah Almighty to help us serve His cause and render our work for His Sake.
If they slander that innocent girl, accusing her of zina, then they are criminals. This is a major sin and an abhorrent forbidden action, because it is a slander against her honor and a transgression of the limits set by Allah. The Qur'an says, "...and those who accuse honorable women but bring not four witnesses, scourge them with 80 stripes and never afterwards accept their testimony. They indeed are evildoers." (An-Nur: 4) In another verse Allah says, "Lo! As for those who slander virtuous, believing women who are careless, cursed are they in the world and in the hereafter. There's will be an awful doom." (An-Nur: 23)
The Prophet (peace and blessings be upon him) said: “Avoid the seven sins that doom one to Hell.” They said: “O Messenger of Allah, what are they?” He said: “Associating others with Allah (shirk), witchcraft, killing a soul whom Allah has forbidden us to kill, except when it is lawful, consuming riba, consuming the orphan’s wealth, running away from the battlefield, and slandering chaste believing women who never even think of anything touching their chastity.” (Reported by al-Bukhari and Muslim)