We hear the deep pain and exhaustion in your request and we are lifting you and your whole family before the Lord together. To love and serve someone who is hateful and unkind in return, who figuratively spits on your kindness, is a heavy and wounding burden, and we grieve with you over the hardness of her heart toward God and toward you.
We want to speak truth in love about what she is saying. When she says she does not need God because He ruined her life by making her disabled and not allowing her to get married and have fun, she is believing a lie about who God is. God did not ruin her life. He formed her with purpose and value. Psalm 139:13-14 tells us that God knit us together in our mother's womb and we are fearfully and wonderfully made. Exodus 4:11 reminds us that it is the Lord who makes the mute, the deaf, the seeing and the blind. And in John 9:1-3 Jesus made clear that a man's disability was not because of his sin or his parents' sin, but that the works of God might be revealed in him. Her disability is not a mistake and it is not a punishment that makes her less worthy of love or of a godly marriage. Her anger is understandable as pain, but it is misdirected at the very One who loves her most and who alone can give her true joy.
We also must address what she means by having fun and not being allowed to get married. We affirm with you that marriage is a beautiful gift from God, a lifelong covenant between one man and one woman, and we pray that if it is God's will she would one day be blessed with a godly spouse who is a believer in Christ, entering into courtship with the goal of marriage that honors Him. But true joy and fun are not found in living apart from God's design. If by fun she means sexual intimacy or living without restraint outside of marriage, scripture calls that fornication and it will never satisfy the soul, but only leave more emptiness. Hebrews 13:4 teaches that marriage is to be held in honor and the marriage bed undefiled. What she needs more than a change in circumstances is a change of heart, because going to church just to check that off the list is not faith at all. God desires not outward religion but a surrendered heart. 1 Samuel 16:7 says man looks at the outward appearance, but the Lord looks at the heart. Without Christ, church attendance cannot save.
You asked what is stopping God from giving all of you a breakthrough and why He has allowed her mind to be disturbed since birth and to get worse. We gently rebuke that way of thinking because it assumes God is withholding good from you or that He is unable to act. Nothing is stopping God. Isaiah 55:8-9 says His ways are higher than our ways and His thoughts higher than our thoughts. He is sovereign, He is good, and He is working even when we cannot see it. Romans 8:28 promises that for those who love God all things work together for good for those who are called according to His purpose. A breakthrough in God's timing may not look like an instant change in her personality, but He is using this long suffering to shape endurance, character and hope in your family if you do not grow weary. Galatians 6:9 urges us not to grow weary in doing good, for in due season we will reap if we do not give up. Her free will and her choice to reject God are real, and God will not force her to love Him, but He is patient, not wishing that any should perish but that all should come to repentance as 2 Peter 3:9 teaches.
How then do we as Christians respond to a family member like this. We respond with the love of Christ, but love is not without truth or boundaries. We are called to bless those who curse us and pray for those who mistreat us, Matthew 5:44, and to not repay evil for evil but to overcome evil with good, Romans 12:21. That means continuing to do kind things without expecting return, speaking with a gentle answer that turns away wrath, Proverbs 15:1, and forgiving as Christ forgave us, Ephesians 4:32 and Colossians 3:13. It also means speaking the truth in love, Ephesians 4:15. It is loving to tell her that her words are hurtful and dishonoring, especially to her mother as she cares for her, for scripture commands us to honor our father and mother, Exodus 20:12, and that kindness matters to God. It is loving to set calm, consistent boundaries about how you will be spoken to, while still showing mercy. It is loving to stop enabling a victim mindset where everything is about herself, and instead point her to Christ who alone can heal her bitterness.
We noticed your request speaks of God but does not mention Jesus Christ, and we want to lovingly say that it is only through Jesus that we have access to the Father and that any of us can be saved or truly transformed. Jesus said in John 14:6, I am the way, the truth, and the life. No one comes to the Father, except through me. Acts 4:12 declares there is salvation in no one else, for there is no other name under heaven that is given among men, by which we must be saved. Romans 10:9 teaches that if you will confess with your mouth that Jesus is Lord, and believe in your heart that God raised him from the dead, you will be saved. This is the hope she needs, and the hope you need as you wait. We cannot argue her into the kingdom, but we can pray fervently that the Holy Spirit will open her eyes to see that God did not ruin her life, but that He loves her, that her value is not in her ability or marital status, and that His grace is sufficient for her, 2 Corinthians 12:9.
We pray together for you now.
Father in heaven, we come before You only in the name of Jesus Christ Your Son, our only hope and mediator. We lift this precious family to You who are weary and desperate for a breakthrough. Lord, have mercy on this daughter who is angry at You. Soften her hard heart, open her eyes to Your love, forgive her for the hateful words she has spoken against You and against her family. Help her to see that You created her with dignity and purpose, that You have not ruined her life but that You desire to give her abundant life in Christ. Deliver her from bitterness and self focus and bring her to true repentance and faith in Jesus for salvation. Heal her mind and emotions as only You can, and give her Your peace and joy that surpasses circumstances.
Father, we lift her family who have been wounded by her unkindness. Give them Your strength to love without growing bitter, to speak truth with gentleness, to set healthy boundaries, and to continue doing good without fainting. Guard their hearts from discouragement and help them to cast all their anxiety on You because You care for them, 1 Peter 5:7. Let Your peace that surpasses all understanding guard their hearts and minds in Christ Jesus, Philippians 4:7. Help them to trust Your timing and Your goodness, to count it joy even in trials knowing You are producing perseverance, James 1:2-4. If it is Your will, bring a godly spouse into her life in Your time, and in the meantime teach her and her family contentment and hope in You alone. We ask all this in the mighty and saving name of Jesus Christ, Amen.
Prayer Focus: God, Thank You for loving me. Thank You for loving me, Jesus. God, I ask You in Jesus’ name please bless me with everything that I stand in need of and everything You want me to have. God bless me to prosper, walk in excellent health, and never stop growing in the love, grace, wisdom, and knowledge of Christ Jesus. God bless me to know You in truth, fall in love with You with all my heart, mind, soul, body, and strength and never fall out of love with You. God, bless me to have an ever growing closer stronger, more intimate relationship with You. Bless me with the love, desire, strength, and the spirit of obedience to always delight myself in You, seek first Your kingdom, Your righteousness, and to always respect and obey You. Bless me to know You, the way You want me to know You. So that I will trust You with my life and anyway that You move in my life. Bless me to trust You with all my heart, lean not to my own understanding, acknowledge You in all my ways, and allow You to direct my footsteps and actions. Bless me with knowledge, wisdom, and understanding in all You have called me to do. 
