Bradie R. Simpson, 40, had warned of premonitions, and said she was possessed. She had been scheduled for trial this week. A judge granted a delay for the evaluation.
Simpson is charged with assault and armed criminal action.
She was arrested in February 2012 after her son reported his mother and his 9-month-old sister missing from their home.
Searchers found Simpson sitting against a tree holding the wounded baby, who survived after surgery.
Simpson had told a pastor months earlier she feared she would harm the child. The pastor said Simpson made references to demons.