Elizabeth, we are with you in spirit, praying for your sister Margaret's healing. We understand your desire to pray fervently for her, and the Holy Spirit can indeed intercede through us with groans that words cannot express as mentioned in Romans 8:26: "In the same way, the Spirit also helps our weaknesses, for we don't know how to pray as we ought. But the Spirit himself makes intercession for us with groanings which can't be uttered." This does not always mean speaking in tongues, yet is always praying by the Holy Spirit. This we hope will encourage you and know that God is using you to make intercession for your sister.
Speaking in tongues, as described in in 1 Corinthians 14:2-4, 1 Corinthians 14:13-14, and 1 Corinthians 14:27-28 is a spiritual gift from the Holy Spirit. However it is regulated and used properly as directed in the scripture. The gift and results are not of our own volition. It is only a gift that God gives through the Holy Spirit. Further information about speaking in tongues can be found in the WEB in 1 Corinthians 12.
But take heart, Jesus said in John 14:13-14: "Whatever you will ask in my name, I will do it, that the Father may be glorified in the Son. If you will ask anything in my name, I will do it." This means if you ask for Margaret's health in Jesus name it is not a vain request. It will be answered, for I know your faith. Further Jesus told us in Mark 11:24: "Therefore I tell you, all things whatever you pray and ask for, believe that you have received them, and you shall have them."
But we tell you that it is not the quantity or the method of your prayers that matters, but the faith behind them. As Jesus told us in Matthew 21:22: "All things whatever you will ask in prayer, believing, you shall receive." Expressing our thoughts and requests to God in a language we understand is more practical and more important, so we can pray for one another in agreement.
Continue to pray for Margaret's healing with faith, and trust that God hears your prayers of Jesus's intercession. May you find comfort in the words of James 5:14-16, "The prayer of faith will save him, and the Lord will raise him up; and if he has committed sins, he will be forgiven. Confess your offenses to one another, and pray for one another, that you may be healed. The insistent prayer of a righteous person is powerfully effective. Elijah was a man with a nature like ours, and he prayed earnestly that it might not rain, and it did not rain on the earth for three years and six months. He prayed again, and the sky gave rain, and the earth produced its fruit."
We continue to pray with you in Jesus' name:
Heavenly Father, we come before you in the mighty name of Jesus, lifting up our sister Margaret. We ask that You touch her body and bring healing and restoration. Give Elizabeth the words to pray, filled with faith and trust in Your goodness. We stand in agreement, believing that Margaret's health is Your will. In Jesus' name, we pray. Amen.