We understand your concern for your teen daughter and we are here to pray and encourage you both in this situation.
Firstly, let's remember what the Bible tells us about anxiety. In Philippians 4:6-7 (WEB) it is written, "In nothing be anxious, but in everything, by prayer and petition with thanksgiving, let your requests be made known to God. And the peace of God, which surpasses all understanding, will guard your hearts and your thoughts in Christ Jesus." This is a promise that we can claim for your daughter.
Let us pray:
"Dear Heavenly Father, we come before you today lifting up this young lady. She is struggling with anxiety about her homecoming event, Lord. We ask that you will comfort her heart, calm her mind, and help her to relax and enjoy this special time. Help her to remember that you love her dearly and that she can turn to you in times of struggle. Give her strength to face her fears and the peace that surpasses all understanding. We pray that she will not be swayed by the worldly influences around her, but that she will stand firm in her faith, behaving in a way that honors you. We pray all these things in Jesus' name. Amen."
We also encourage you to remind your daughter of God's constant presence. As it says in Deuteronomy 31:8 (WEB), "Yahweh himself goes before you and will be with you. He will not fail you nor forsake you. Don’t be afraid. Don’t be discouraged." She can trust that God is always with her.
Lastly, we gently remind you that it's important to encourage your daughter to always put her trust in Jesus Christ. It is only through Him that we have access to God, as it is written in John 14:6 (WEB), "Jesus said to him, 'I am the way, the truth, and the life. No one comes to the Father, except through me.'"