Your love for your sister and your desire to bring her before the Lord is a beautiful thing, and God hears that kind of prayer. You are asking for the very things Scripture encourages us to seek for those we love, guidance, protection, and a heart that stays close to Jesus.
It helps to remember what the Bible says about temptation. God is not tempted by evil and He does not entice anyone to do evil. When there is a solicitation to do what is wrong, that invitation does not come from God, it comes from the enemy. God does allow tests in our lives, not to make us fall, but to give us an opportunity to choose whether we will respond according to the flesh or according to the Spirit. So when your sister faces pressure or an influence that pulls her toward evil, that pull is not from the Lord, and you can pray with confidence that God wants to give her strength to turn away from it.
You also do not need to be discouraged if she does face temptation. Being tempted is not itself sin. We all experience it, and even Jesus was tempted, yet without sin. Sin comes when a person gives in to the desire of the flesh and follows the path that the enemy suggests. That is why your prayer for her to make good choices and to have the Holy Spirit with her is so important. The desire of the flesh conceives and brings forth sin, and sin when finished brings death, but God provides a way to stand against it.
Scripture also teaches that we keep ourselves in the love of God. We cannot walk away from the Lord and from His ways and still expect to live under His protection. His protection and guidance are enjoyed as we stay close to Him. That is why the fear of the Lord is described as hating evil. A healthy love for God includes a hatred for what God hates and a willingness to depart from evil rather than tolerate it or make peace with it. Evil always asks to be tolerated and to be compromised with, but wisdom says to turn from it completely.
Part of that protection comes from the company we keep and the counsel we listen to. Proverbs warns again and again about peer pressure to do evil and about the person who leaves upright paths to walk in darkness. The promise is that if we remember God's word and keep His commands in our heart, and if we trust in the Lord with all our heart instead of leaning on our own understanding, and acknowledge Him in all our ways, He will direct our paths and preserve us from the way of the evil person. God also promises wisdom to anyone who asks Him for it, and He gives generously. You can ask Him to give your sister a clear mind to discern what is good and to love what is good, and to be simple concerning evil rather than curious about it.
So we join you in praying for her. We ask the Lord to watch over her physically, spiritually and mentally, to guard her from harm, to remove evil influences from around her, and to set her feet on a right path. We ask Him to fill her with His Holy Spirit, to help her see the light of Christ, to know deeply that she is loved and cared for as a child of God, and to grow in her love for Him and commitment to His ways. We trust in the covering of the blood of Jesus over her life from head to foot, not as a formula, but as confidence in what Christ has done to redeem and cleanse and keep those who belong to Him.
May the Lord strengthen her as she walks in this world, keep her heart pure and holy toward Him, and hold her hand every step of the way. In Jesus name we pray, amen.