We are truly sorry to hear about the strain in your relationship with your best friend. It's commendable that you are concerned about her path and the outcome. We are called to pray for one another, and your faithfulness in doing so is evident. Let's first address your request for her change in direction.
The power of prayer is immense, and we are instructed to pray for others. In James 5:16 (WEB), it says, The effective, earnest prayer of a righteous man accomplishes much. We can take heart that our prayers do make a difference. We should also remember God's promise to us in 2 Chronicles 7:14 (WEB), if my people, who are called by my name, will humble themselves, pray, seek my face, and turn from their wicked ways; then I will hear from heaven, will forgive their sin, and will heal their land. This is a reminder that repentance is a crucial part of restoration.
Regarding the relationship, it is important to remember what we are told in Romans 12:18 (WEB), If it is possible, as much as it is up to you, be at peace with all men. We should actively seek peace and reconciliation, but also remember that it is not always possible if the other person is not willing. God will help you in this relationship.
We are praying:
Dear Heavenly Father,
We lift up our sister and her best friend to You, asking for Your divine intervention. Lord, You know the path her friend is on, and we ask that You draw her back to You, changing her heart and mind. Turn her path, Lord, and help her to see Your truth in Jesus Christ. In the name of Jesus we pray for her friend to believe in Jesus and turn from her sin.
We also pray for their relationship. Lord, we ask that You would heal any wounds between them and draw them closer together than ever before, but only if that is in your plan for them. Help them to reconcile and to walk in a manner worthy of You, fully pleasing, being fruitful in every good work, and increasing in the knowledge of God, according to Colossians 1:10 (WEB). In Jesus Name we pray.
Finally, we encourage you to remain steadfast in prayer and faithful to God's will. Remember that God works all things together for good for those who love Him and are called according to His purpose, according to Romans 8:28 (WEB). Keep trusting in Him, and He will direct your paths. We are praying for you and your best friend, trusting that God will hear and answer our prayers according to His will so they can glorify Him.