We understand that you're going through a difficult situation, but we need to address several things in your prayer request that do not align with biblical principles.
Firstly, we must remember that God's will should be our ultimate desire, even if it doesn't align with our initial wants. In this case, you're asking for an ex-girlfriend to return, but it's crucial to seek God's will for your life first. It might be His will for you to move on and trust Him with your future. As it is written, "For I know the thoughts that I think toward you, says Yahweh, thoughts of peace, and not of evil, to give you hope and a future." Jeremiah 29:11 WEB.
Secondly, it's important to address the issues of substance abuse and sexual immorality. We commend you for standing firm against these things, as it is clear that God calls us to flee from sexual immorality and honor Him with our bodies.
"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." 1 Corinthians 6:18-20 WEB
We encourage you to continue praying for her salvation and deliverance from these issues. "If the Son therefore will make you free, you will be free indeed." John 8:36 WEB.
Moreover, it's important to clarify that the goal of a relationship should be marriage, as it is the only biblical context for a romantic relationship. If she is not a believer in Jesus Christ, then this would not be a relationship that is encouraged.
"Do not be unequally yoked with unbelievers, for what fellowship have righteousness and iniquity? Or what communion has light with darkness?" 2 Corinthians 6:14 WEB
Lastly, we want to encourage you to keep your focus on Jesus Christ. It is only by His name that we can be saved.
"in whom we have boldness and access in confidence through our faith in him." Ephesians 3:12 WEB
"There is salvation in none other, for neither is there any other name under heaven, that is given among men, by which we must be saved!" Acts 4:12 WEB
Let's pray together:
Heavenly Father, we come before You, lifting up this dear one who is struggling. We pray for Your will to be done in his life and for his ex-girlfriend. If it is Your will, restore their relationship under God appointed standards, serving You together. Help them to remain pure and flee from all sexual immorality and substance abuse. Deliver her brother from his struggles, and bring him to salvation. Give them both a new heart and a new spirit, that the old things will pass away and all things become new. Help him to fix his eyes on Jesus, the author and perfecter of our faith. In Jesus' name we pray. Amen.
Prayer Focus: God, Thank You for loving me. God, I ask You in Jesus’ name please bless me with everything that I stand in need of and everything You want me to have. 
