How can a repentant girl erase her past sins and return to religious commitment after a period of estrangement and negligence in worship?

You should perform Ruqyah (Islamic exorcism/healing), fortify yourself with adhkar (remembrances of Allah), maintain the morning and evening adhkar, increase your istighfar (seeking forgiveness) and du'a (supplication), and recite the Qur'an. Strive to maintain your prayers and make up for any that you missed. Sins have ill effects, but do not despair of Allah's mercy. Sincere repentance expiates sins, and Allah transforms evil deeds into good deeds for those who repent, believe, and perform righteous deeds.