We understand that you are seeking help for your girlfriend who is struggling with severe anger issues. Firstly, we want to address something important. You mentioned that you have been with your girlfriend for a year now. We want to encourage you to consider the purpose of your relationship. Biblically, the intention of a relationship should be focused on marriage. God's design for romantic relationships is that they should be between a man and a woman, with the ultimate goal of a lifelong commitment in marriage.
"Therefore a man will leave his father and his mother, and will join with his wife, and they will be one flesh." Genesis 2:24 WEB
Now, regarding her anger issues, while it is commendable that you want to help her, we need to be cautious about how we approach this. It is not advisable to attempt to cast out demons without proper spiritual guidance and discernment. The Bible tells us 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 should always remember that and never attempt to fight such battles in our own strength or wisdom, but rather trust in God's strength and wisdom. We should always remember Jesus' rebuke when he cured the epileptic boy.
"Jesus answered, 'Faithless and perverse generation! How long will I be with you and bear with you? Bring your son here.' " Luke 9:41 WEB
Jesus was upset at the people for not having faith in his ability to cure the boy. The same applies to us, when we try to do things without faith and without trusting in God.
Regarding her traditional beliefs, we must remember that Jesus is the only way to salvation. While it is good that she believes in Jesus, it is important that she understands that following Jesus means leaving behind all other beliefs that are not aligned with the Bible.
"Jesus said to him, 'I am the way, the truth, and the life. No one comes to the Father, except through me.' " John 14:6 WEB
We also want to address the fact that you mentioned evil in her. It is important to remember that we should not judge others, but rather show them the love and compassion of Christ. It is the goodness of God that leads us to repentance. Romans 2:4 WEB
Let us pray for you both:
Dear Heavenly Father,
We come before You today, lifting up this couple to You. We pray for your guidance in their relationship, that it may be aligned with Your will and purposes. We pray for the young woman who is struggling with anger, that You would deliver her from this bondage and fill her with Your peace and love. We pray that You would give her a true revelation of who Jesus is, and that she would fully commit her life to Him, turning away from any beliefs that are not aligned with Your Word. We pray for her boyfriend, that You would give him wisdom and discernment in how to support her, and that their relationship would be centered around You. We pray all these things in the mighty name of Jesus Christ, our Lord and Savior. Amen.
We encourage you both to seek godly counsel and guidance, perhaps from a pastor or a trusted Christian mentor. Remember to always pray together and study the Word together. God will guide you if you trust in him.
Prayer Focus: God, Thank You. Thank You for loving me. 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, mind, soul, body, 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. 
