Board Thread:Speculation House/@comment-1292715-20181223044830/@comment-26018514-20190429161039

She didn't lose the arm the glove was on, she lost the arm the grimm was in at the time. The entire scene where Cinder was hit by the SEW blast was mirrored in Ruby's eye, so the arm she lost is the one farthest away from Ruby at the time, because the Grimm was trying to escape the SEW from the moment Cinder said "what!" and her "mask" shut off before Ruby attacked.