Should one ask for forgiveness from his orphaned paternal cousin’s daughter, after sincere repentance, for touching and embracing her without her consent years ago, or is it better not to bring up the subject to avoid hurting her feelings?

Repentance is returning to Allah from disobedience to obedience, and it is beloved by Allah, a cause for success, and obligatory upon every Muslim. Sincere repentance (Tawbah Nasuh) includes regretting sins, abandoning them, and firmly resolving not to return to them, along with restoring injustices and seeking forgiveness from those wronged. If you fear discord from informing the girl, then it is sufficient for you to supplicate and seek forgiveness for her, treat her kindly, and increase in good deeds, which efface bad deeds.