We are truly sorry to hear about your mom's condition, and we stand with you in prayer for her healing and comfort. We believe that God has the power to heal, and we trust in His will for your mom's life.
Firstly, we want to address the phrase "healing has already taken place." While it's true that by Jesus' stripes we were healed (1 Peter 2:24 WEB), this healing was purchased for us and is available to us, but it is not automatic. We must ask and have faith and it is only by the name of Jesus that we can be saved or receive any blessing from God. God's will is not for all believers to be healed in the same way. The Apostle Paul prayed and asked God for healing and God said no. 2 Corinthians 12:7-9 (WEB) says:
"Because of the exceeding greatness of the revelations, that I should not be exalted excessively, there was given to me a thorn in the flesh, a messenger of Satan to torment me, that I should not be exalted excessively. Concerning this thing, I begged the Lord three times that it might depart from me. He has said to me, 'My grace is sufficient for you, for my power is made perfect in weakness.' Most gladly therefore I will rather glory in my weaknesses, that the power of Christ may rest on me."
So we pray for God's will, recognizing that His grace is sufficient for us and His power is made perfect in our weakness.
Let's pray together:
"Father, we come before You in Jesus' name, lifting up our sister's mom to Your throne of grace. We ask for Your healing touch upon her body, especially her right knee and the effects of the stroke. We pray that You would reduce the pain, and give her rest and comfort. Help her to trust You in this difficult time.
We also pray for strength and grace for her family, that they would be able to support and care for her in this time of need. Help them to trust in You and to draw near to you through prayer and reading Your word.
Ultimately, Father, we ask that Your will be done in her life. If it is Your will, please bring healing to her body. But if not, give her the grace and strength to endure, just as You did with Paul. Help us all to trust in You more.
We ask all these things through Jesus Christ our Lord. Amen."