What dissimilarities I noticed:
Red sweater girl has a different brow shape from the missing girl. She has thick, slightly arched brows while the missing girl has plucked and raised eyebrows.
Red sweater girl has a slightly wide ovate face with a slightly square chin shape, while the missing girl has more of a diamond shaped face with higher cheekbones and a heart chin shape.
Red sweater girl has bigger breasts than the missing girl.
Red sweater girl has a different skin undertone.
Missing girl has a smaller, shorter nose.
Missing girl also looks younger, but she could've aged in that pic.
Similarities are.. I think their eye shape is similar. But missing girl has more almond shaped eyes while this red sweater girl has rounder eyes.