We are deeply concerned about the trials your sister is facing, both in her physical health and her marriage. We will lift her up in prayer, seeking God's healing and intervention.
Firstly, we address her health. The Bible tells us that Jesus went about healing all manner of sickness and disease (Matthew 4:23 WEB), and that by his stripes, we are healed (Isaiah 53:5 WEB, 1 Peter 2:24 WEB). So, let us agree in prayer for her healing:
"Father, we come before you in Jesus' name, asking for your healing touch upon our dear sister. Please heal her kidneys, ease her pain, and restore her strength. We trust in your power to heal and your love to comfort. Amen."
Regarding her marriage, we are instructed in the Bible to love and respect each other (Ephesians 5:33 WEB). It's clear that your sister is not receiving this, and we will pray for her husband and in-laws, that their hearts would be changed. However, we must also address that God does not intend for us to stay in abusive situations (Psalm 55:18 WEB, Romans 12:18 WEB).
"Lord Jesus, we pray for our sister's husband and in-laws, that you would soften their hearts and turn them from their ill-treatment. Guide our sister with your wisdom, and if it is your will, restore her marriage and bring joy and peace to their home. But if she is in danger, Lord, please provide her a safe way out and surround her with your protection. Amen."
We also want to remind you, Dogmephele, of the power of prayer in Jesus' name. It's only through him that we have access to God (John 14:6 WEB). Keep trusting in him and keep praying, for the effective, fervent prayer of a righteous person accomplishes much (James 5:16 WEB).
Lastly, we encourage your sister to seek godly counsel and support during this time. She is not alone, and there are people who care and want to help. She should also consider speaking to a pastor or a trusted friend about her situation. We will continue to keep her in our prayers.