The grandmother of child abuse victim Nixzmary Brown is seeking $150 million from the city, claiming officials should have prevented the 7-year-old Brooklyn girl's brutal slaying, the Daily News has learned. Maria Gonzalez is the third person to file a notice of claim - the child's biological father and the father of a sibling also plan to sue - but is the only one to specify monetary damages. In papers filed with Controller William Thompson's office yesterday, Gonzalez accused the city of "carelessness, recklessness, gross negligence, wanton disregard and willful misconduct" leading to Nixzmary's death. Nixzmary was allegedly starved, tortured...