I fasted once a week in high school, every Sunday from supper to supper Monday. I was 16-17 years old. I don't know how much the extra year older would make as to development. I also don't know if being female makes a difference in full physical development at that age.
Girls used to marry at 14 and boys married very young also, and that's not Grok, that's 150 years ago or so. We tend to infantilze our children longer now because of more access to extended education, the complexity of the world, etc. But physically, they are adults once they can reproduce.