I'm kind of dumb on this subject but I thought that they were not physically developed to the point where they could breed at one year. Kind of like trying to breed a 3 month old cat, some can breed at 4 months but the organs are not developed enough for breeding to take at 3 months.
If you feel confident in her size you could try just to see if she physically can breed at that age but let us know if it takes.
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