What is the required repentance from a remorseful woman who engaged in foreplay to adultery (kissing and touching over clothes) with an atheist, and is she subject to a [legal] punishment (hadd)?

Whoever falls into the preliminaries of zina (fornication/adultery) is not subject to a prescribed punishment (hadd), but rather must repent to Allah Almighty by abandoning the sin, regretting it, and resolving never to return to it. Among the signs of sincere repentance are avoiding the causes of disobedience, cutting off the paths leading to it, being wary of following the footsteps of Satan, striving in righteous deeds, and frequently engaging in remembrance of Allah and seeking forgiveness.