We understand that you are going through a troubling time, feeling under spiritual attack after your fiancé set boundaries with certain individuals. Firstly, we want to remind you that our struggle is not against flesh and blood, but against the rulers, against the authorities, against the powers of this dark world and against the spiritual forces of evil in the heavenly realms Ephesians 6:12 WEB.
We must address a few things before we begin our prayer. It is so important to know the name of Jesus is the only name by which we can be saved. And there is salvation in no one else, for there is no other name under heaven given among men by which we must be saved Acts 4:12 WEB.
The situation you are describing involves witchcraft and curses, which are clearly condemned in the Bible. Deuteronomy 18:10-12 WEB Let no one be found among you who sacrifices his son or daughter in the fire, who practices divination or sorcery, interprets omens, engages in witchcraft, or casts spells, or who is a medium or spiritist or who consults the dead. Anyone who does these things is detestable to the Lord. God is on your side and He promises us in Romans 8:31 WEB that if God is for us, who can be against us?
It is encouraging to hear that your fiancé has set boundaries. However, we must also address that the Bible teaches us to be equally yoked with fellow believers in Christ. 2 Corinthians 6:14 WEB Do not be unequally yoked with unbelievers. For what fellowship has righteousness with unrighteousness? And what communion has light with darkness?
As the fiancée, make sure the focus is on marrying a follower of Jesus Christ. If there is anything happening that should not be happening physically, please discontinue until marriage. Fornication is sex outside marriage and should be avoided. Sex should be avoided until you are married. Does the fiancé believe the Bible's teaching about witchcraft and does the fiancé have a personal relationship with Jesus Christ?
Let us pray together:
Dear Heavenly Father,
We come before You in the mighty name of Jesus Christ, lifting up our sister who feels under attack. We pray that You would surround her with Your hedge of protection, and that no weapon formed against her would prosper Isaiah 54:17 WEB. We rebuke any evil directed towards her, and declare it null and void in Jesus' name.
We pray for her fiancé, that You would draw him closer to You, and that he would seek Your face continually. We pray that their relationship would be centered on You, and that they would pursue purity and holiness together.
We pray for those practicing witchcraft, that You would have mercy on them, and that they would come to know the truth of the Gospel. We pray that they would repent and turn to You, the only true God.
We ask all this in the powerful name of Jesus Christ, our Lord and Savior. Amen.
Prayer Focus: God, Thank You for loving me. Thank You for loving me, Jesus. God, I ask You in Jesus’ name bless me with everything that I stand in need of and everything You want me to have. Bless me to know You in truth, fall in love with You with all my heart, soul, mind, and strength and never fall out of love with You. Bless me to have an ever growing closer stronger, more intimate relationship with You. Bless me with the love, desire, strength, and the spirit of obedience to always delight myself in You, seek first Your kingdom, and Your righteousness. Help and strengthen me God to always respect and obey You. Bless me to trust You with all my heart, acknowledge You in all my ways, and lean not to my own understanding. 
