What action is obligatory to get rid of sin and the fear of punishment after repenting from practicing tribadism, knowing that seeing the friend stirs up painful memories?

What you did is a grave sin, an evil opened by Satan and a desire of the self. However, Allah has guided you to repentance, remorse, seeking forgiveness, and abandoning the sin. Continue seeking forgiveness, feeling remorse, and fearing Allah. Sever your connection with the girl, adhere to acts of obedience and worship, and abandon bad company and unlawful amusements. If you are sincere in your repentance, then Allah will accept it and replace your bad deeds with good ones. Allah Almighty says: "Except for those who repent, believe and do righteous work. For them Allah will replace their evil deeds with good deeds. And ever is Allah Forgiving and Merciful." [Al-Furqan: 70].