A dad walked into a Brooklyn apartment on Friday and found one daughter covered in blood holding a meat cleaver and the other writhing on the floor in pain, authorities said. Amy You, 35, is accused of attacking her 36-year-old sister with the meat cleaver during a bloody brawl in her Sunset Park apartment on 49th Street at around 10:45am, according to the criminal complaint. You allegedly slashed her older sibling in the face, hands, arms, leg, shoulder and stomach, authorities said. More on this from Pix 11…