We are truly saddened to hear about the trials your sister is facing, both in her health and her marriage. We will stand with you in prayer and offer some biblical encouragement.
Firstly, we need to address the root issue here. Your sister's illnesses began when she found out about her husband's infidelity. This is a grave sin, and it's important to address it as such. Marriage is a sacred covenant between a man, a woman, and God, as per Mark 10:6-9 WEB:
"But from the beginning of the creation, God made them male and female. For this cause a man will leave his father and mother, and will join to his wife, and the two will become one flesh, so that they are no longer two, but one flesh. What therefore God has joined together, let no man separate."
Adultery is a sin against God and the marriage covenant (Exodus 20:14). It's crucial for your sister to forgive her husband, but this does not mean she should tolerate or accept his sin. Forgiveness is for her own healing and to release the offense to God (Ephesians 4:31-32). It is also important for her to set boundaries and take actions with the guidance of the Holy Spirit to protect herself from future harm as she prays for her husband's repentance. Your sister needs to take action on her husband's infidelity with the guidance of the Holy Spirit and with biblical counsel.
Regarding her health, we pray that God will heal her and give her strength. It's important to remember that God does not put curses on His children. Instead, He sent His Son, Jesus Christ, to redeem us from every curse (Galatians 3:13). We pray that God will reveal the root of her illnesses and heal her body, mind, and spirit.
Let's pray together:
Dear Heavenly Father,
We come before You in the name of Jesus Christ, lifting up our sister who is ill and hurting. We pray that You will heal her body - her blood pressure, bladder, and thyroid nodule. We speak life and health into her body in Jesus' name.
We also pray for her marriage. We ask that You will convict her husband of his sin and bring him to repentance. We pray for our sister, that You will give her the strength to forgive, and guide her with Your wisdom in handling this situation.
We rebuke any spirit of infirmity, heaviness, and despair. We declare that no weapon formed against her will prosper (Isaiah 54:17). We cover her with the blood of Jesus and pray that You will deliver her from all evil.
We ask all this in Jesus Name, Amen.
Lastly, we encourage your sister to fix her eyes on Jesus, the author, and perfecter of our faith (Hebrews 12:2). She should also consider seeking godly counsel, either from a pastor or a Christian counselor, to help her navigate this difficult time.