Ramaddox, you sound like a very stable force in her life, and she needs someone like that. Really pray before you cut your niece out of your life...she can't help where she finds herself. You can keep in touch through mail or phone calls. I'm sure she will miss you terribly and it will be something else she will need to deal with if you just walk out of her life...
Father, I just plead the blood of Jesus on this niece and ask for special protection to be upon her. I break the curse of suicide off her life, and I bind her to the life of light which is Jesus. I pray for dreams and visions and even visitations of angels and Jesus to minister to her. I speak the boldness of the Holy Ghost in her, and let the love cover her like a shield. I just ask for ridiculous favor for this niece, and that I declare that no weapon formed against her shall prosper, and that there shall no evil befall her nor any plague come near her dwelling. I ask for the heart of this grandmother to be turned around and that the heart of Jesus would be given her towards this child. I bind the spirit of unbelief over her life, and ask that her heart be turned and engaged to hear the word of the God, the good news of Jesus Christ. Thank you for the blood of Jesus and I plead the blood upon her, around her, between her and evil and the author of evil. Thank you Jesus for a grandmother who loves her and walks before her in love and grace of God. In Jesus' name I pray, Amen.