At long last, some peace. A cousin of Angelica Castillo, the four-year-old girl found strangled and bound in a cooler along a New York City highway in 1991, confessed Saturday to killing the girl and sexually abusing her. Conrado Juarez, 52, told police he sexually assaulted the girl while staying at her family’s crowded Queens apartment, and reportedly strangled her with a pillow when she tried to scream. The 22-year-old cold case got its first big break in decades this summer when a tipster came forward with information about Angelica’s sister. The tip eventually led police to the girl’s mother, who failed to report her missing because she feared the girl’s abusive father.