My brother was in coma 45 days saw the Gates of Heaven and Hell, he was saved and baptized afterwards , lived a very different life before, you need to go somewhere private , get on your knees , talk to God and ask him to remove any thing bad like grudges, hate ect from your heart , then ask him to heal your sister, He hears if your heart is clean-God Bless you for prayer request

John 9:31
Now we know that God heareth not sinners: but if any man be a worshipper of God, and doeth his will, him he heareth.