Is it a religious obligation to inform a suitor that a girl has been subjected to sexual harassment and penetration, or does referring the suitor to inquire about the family in general absolve one of responsibility?

There is no obligation to inform the suitor about what happened to the girl, whether it was harassment or fornication. Rather, she should be covered, and there should be caution against spreading such talk, due to the absence of a recognized benefit and the presence of harm and scandal therein, and because of Umar ibn Al-Khattab's hadith regarding this. If the girl marries and her virginity was lost due to harassment, she is not required to inform her husband, knowing that virginity can be lost due to reasons other than fornication.