UNIONTOWN, Pa. (AP) -- One of two sisters pleaded guilty to her role in a purse-snatching that broke the hip of an 82-year-old Pennsylvania woman who died months later, but a judge refused to accept the other sister's guilty plea Monday after she claimed to have no part in planning the crime. Brittany Boyd, 25, pleaded guilty to charges including robbery and aggravated assault. Her victim, Mary Margaret Yourchik, was buying birthday candles for her daughter and Easter candy for her grandchildren when she was robbed outside a southwestern Pennsylvania Wal-Mart. Boyd told the judge she was a heroin addict looking for money when she took the purse from Yourchik's shopping cart outside the Fayette County store on March 22, 2012. "She chased me back to my car and tried to grab the purse from me," Boyd told Fayette County Judge Steve Leskinen. "When that happened she fell and I just drove off." Her sister, Jenna Boyd, 26, also hoped to plead guilty to charges of conspiracy, theft and child endangerment, because three of her and her sister's children were in the car at the time of the robbery. But Leskinen refused to accept the plea after Boyd claimed to not have advance knowledge of the crime. Jenna Boyd, also a heroin addict, told the judge she thought they were to meet their drug dealer in the parking lot. "We were driving around and she jumped out of the car," Boyd said, referring to her sister. "I never participated in it." Yourchik suffered a stroke in June while recovering from the broken hip and died in a nursing home in November. District Attorney Jack Heneks didn't add homicide charges against the sisters after reviewing Yourchik's medical records.