An 89-year-old woman was arrested on Thursday after allegedly killing another elderly woman in a fight at an old people’s home in Kwun Tong.The suspect and the 85-year-old woman, both residents of the home on the ground floor of Tin Kei House, Shun Tin Estate, got into a physical fight at about 5.15pm, a police spokesman said.The younger woman lost consciousness after the clash, and was taken to United Christian Hospital.At about 7pm, she was declared dead.The older woman was later arrested on…