Mentally unfit mother to an Autistic Child. Doing nothing in Child's best interest, how do I prove she is unfit?

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She is constantly giving me conflicting stories regarding our daughter and her schooling (she is 2.5 but in a program for Autism), her health, everything! I don't get a straight story from her. Her parents had her evaluated at 13 because she liked to hurt small animals and had an extreme anger/temper problem. She brags about how she lied her way out of having to talk to the physicatrist. She was physical with me in our relationship, even getting caught on tape throwing food at me and she harrassed me on the phone at work to the point of her getting fired! I am extremely concerned for my daughter. Her mother (my childs maternal grandmother) even told me that whatever happened, she would have to take her daughters side! (they live together) She has told me that she doesn't agree with her daughters way of parenting.