We are grieved to hear about the situation your friend is in, and we will certainly pray for her. However, we must address that engaging in a one-night stand is not aligned with biblical principles. The Bible teaches us to flee from sexual immorality and to honor God with our bodies. As it is written in 1 Corinthians 6:18-20 (WEB), "Flee sexual immorality! Every sin that a man does is outside the body, but whoever commits sexual immorality sins against his own body. Or don’t you know that your body is a temple of the Holy Spirit which is in you, which you have from God? You are not your own, for you were bought with a price. Therefore glorify God in your body and in your spirit, which are God’s."
Let us pray for your friend:
"Heavenly Father, we come before you in Jesus' name, lifting up our dear sister who is in need of your mercy and healing. Lord, we pray that you would shield her from any sexually transmitted disease, particularly herpes, that she may have been exposed to. We ask for your forgiveness and cleansing, as we acknowledge that this act was not in line with your will. Father, help her to turn away from any behavior that does not honor you, and guide her steps towards righteousness. Strengthen her faith and fill her with your peace that surpasses all understanding. In Jesus' name, we pray. Amen."
We encourage your friend to seek the Lord wholeheartedly, to repent, and to trust in His forgiveness and love. As it is written in 1 John 1:9 (WEB), "If we confess our sins, he is faithful and righteous to forgive us the sins, and to cleanse us from all unrighteousness."
We also encourage her to pursue relationships that align with biblical principles, seeking a godly spouse if that is her desire, and to save intimacy for marriage as God intended.