The burden you carry is heavy indeed, and the words you hear hour by hour have wounded your spirit. To be told daily that you are not ok within yourself, that you cannot handle the world now or when your grandmother is gone, that you will be homeless, is to live under a cloud of fear. And you have done well to bring this before the Lord Jesus and to ask Him to show you the truth, for He alone is Savior and He alone speaks truth over you.
What you describe is not the voice of truth but the voice of fear. There is a fear which is healthy, a fear of sinning against God and a holy reverence for Him, which makes a man happy. But there is another fear which brings a snare, the fear of man, and the fear that something evil is about to happen. Your grandmother's words, repeated every hour, stir that tormenting fear in you. They tell you that you are helpless and alone, that she is the only one you can trust, and that the future holds only ruin. Such words, even if spoken from her own anxiety about death and about leaving you, do not build up. They weaken the hands and dishonor God, who says to His people, Fear not.
The Scriptures speak plainly to this condition. The Lord says, Fear not, thou worm Jacob, I will help thee, saith the Lord, and thy Redeemer the Holy One of Israel. And again, Fear not, for I am with thee, be not dismayed, for I am thy God, I will strengthen thee, yea, I will help thee, yea, I will uphold thee with the right hand of my righteousness. The fear of death and the fear of what shall be after is natural to man, but it is not necessary to the saint. Christ has come to deliver those who through fear of death are all their lifetime subject to bondage. When that fear is used to control another, it answers no good purpose, it only keeps the soul in bondage.
You ask if this is manipulation. I will not give a clinical label from a distance, but I will say this plainly. Speech that is constant, negative, and that tells you that you cannot live without one person, that isolates you from others by saying none else can be trusted, and that predicts your failure and homelessness, is controlling speech. It keeps you dependent and afraid, rather than pointing you to Christ and to a sound mind. It is the snare of the fear of man. God does not speak to you in that way. He does not say you are unable and forsaken. He says He will put strength in you.
You are a grown adult and you have taken up the holy duty of caring for your grandmother, and that is honorable in the sight of God. To honor her does not mean to receive as truth every fearful word she speaks. You can honor her by caring for her needs with patience and kindness, and at the same time you must guard your own soul by hearing what God says about you.
Consider these helps, dear soul, though weary:
First, take your identity from Christ, not from these daily accusations. You are not what constant criticism says you are. If you are in Christ, you are His, redeemed, and He will help you. Labor to get rid of fear by looking to Him often, as one using the telescope to see the promises more clearly.
Second, do not walk alone. The word that you can trust no one but her is itself a sign that you need other voices. Go to a faithful pastor or elder, a mature believing woman in your church, and share plainly what you hear and what you carry as a caretaker. The caretaker's work is wearying verbally and emotionally, and God has placed us in a body so that burdens are borne together. You need respite, counsel, and prayer from those who can see your situation with clear eyes.
Third, set quiet and loving boundaries. It is right to say in gentleness, I love you and I will care for you, but I cannot receive these words about my future every hour. Then turn your mind to Scripture. When the prediction comes that you will be homeless or unable, answer it inwardly with, My God shall supply all my need, and He will uphold me.
Fourth, remember that fear dishonors our holy religion in the eyes of others and dishonors Christ in our own hearts. Do not let fear make you dishonor Him by believing you are forsaken. Stand still and see the salvation of God. He has not left you to handle the real world in your own strength. He will handle it with you.
I will pray for you now. O Lord Jesus Christ, Thou who art our only Savior, look upon this weary caretaker. Thou knowest the weight of hourly words and the sting of being told I cannot stand. Speak Thy Fear not over this soul. Show this dear one the truth as they have asked, that they may know what is from Thee and what is not. Put strength in them. Help them to fear Thee in holiness and not to fear man. Provide trusted helpers, a church family, and rest for body and soul. Uphold them with Thy righteous right hand, and give them a prepared heart that need not fear death nor the days to come, for Thou art with them. Amen.
Keep close to Christ, keep in the Word, and keep counsel with godly saints who can walk with you in wisdom.
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. 
