Ji Rongxinyue was not short. Standing at 1.27 meters tall, she was considerably taller than the average height of 1.16 meter for six-year-old girls. Especially considering she had only recently celebrated her fifth birthday, her height was noticeably advanced for her age. However, this wasn't necessarily a good thing.
Having been born in a low gravity environment, her bone density was lower than normal. The difference wasn't massive, as the strength of human genetic inheritance wouldn't cause a drastic change within one generation, but beyond bone density, there were other issues to consider.