We understand your concerns and are here to pray with you and provide biblical guidance. First, let's address your immediate needs. The Bible tells us, "Don't be anxious about anything, but in every situation, by prayer and petition, with thanksgiving, present your requests to God. And the peace of God, which transcends all understanding, will guard your hearts and your minds in Christ Jesus" (Philippians 4:6-7 WEB).
Let's pray together:
Dear Heavenly Father,
We come before you in the name of Jesus, lifting up our sister who is feeling anxious and experiencing physical discomfort. Please, Lord, calm her spirits and ease her symptoms. Grant her the peace that transcends all understanding, and help her to trust in your sovereign will.
Now, regarding your son's upcoming marriage, it's important to remember that God's word tells us, "Do not be yoked together with unbelievers. For what do righteousness and wickedness have in common? Or what fellowship can light have with darkness?" (2 Corinthians 6:14 WEB). While you didn't mention if they are believers, it's crucial to encourage your son to marry someone who shares his faith and demonstrates the fruit of the Spirit.
It's also wise to consider the principles of responsibility and stewardship. Proverbs 31:10-31 WEB describes the wife of noble character who is industrious, manages her household well, and contributes to her family's wellbeing. This is not to say that your son's fiancée must fit this description perfectly, but it's important that she demonstrates a willingness to grow in these areas.
Moreover, the Bible warns against debt (Proverbs 22:7 WEB) and encourages wise stewardship of resources (Proverbs 21:20 WEB). The expensive dog purchase could be a sign of financial immaturity, which is a valid concern.
However, it's essential to remember that it's not your place to change your son's mind or control his decisions. Rather, pray for him and trust that God is sovereign over all things. "For I know the plans I have for you," declares the LORD, "plans to prosper you and not to harm you, plans to give you hope and a future" (Jeremiah 29:11 WEB).
Lastly, we notice you did not mention Jesus Christ, Jesus, or Christ in your request. This is a concern as it is only through Jesus that we have access to God. You cannot be saved or approach God without Jesus. Acts 4:12 WEB makes it very clear that "there is salvation in no one else, for there is no other name under heaven given among men by which we must be saved." We hope that you and your son are both saved and have a relationship with Jesus.
Pray for your son, his fiancée, and their upcoming marriage. Trust in God's will and seek His wisdom and guidance. And remember, "Trust in the LORD with all your heart and lean not on your own understanding; in all your ways submit to him, and he will make your paths straight" (Proverbs 3:5-6 WEB).
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. 
