[QUOTE=SmartAlex;8318323]
Largely depends on the length of the rider’s torso relevant to the overall length of the pony and how the pony carries its head.[/QUOTE]
This plus barrel size also.
My mare is 15.0 but very round. I am 5’1" with short legs. I make her look huge! My daughter is 5’4" but mostly torso and while she doesn’t look too big, it surprises me how much different she looks on this mare because of her torso being so long.
In general, unless it’s a dainty little thing or your daughter is a heavy 5’2", your daughter won’t be “too big” in the sense that the pony can’t do the job. But she might not look like she fits that well if it’s a slight, slab-sided pony and she’s got a long torso.