London - Two teenage sisters were jailed yesterday for killing a frail pensioner who had befriended them and given them sweets. Kellie Lyons (17), was ordered to serve 10 years' youth detention for the manslaughter of Ms Rose Mackenzie (87), at her home on the Woodberry Down Estate, Manor House, north London, in February, and eight years to run concurrently for robbery. Her sister Jean (19), was ordered to serve eight years for the same crime and six years concurrently for robbing Ms Mackenzie.