I've found that there's not even a real correlation between affluence and horse-girlitis as some young girls only ride a few times a year but still have their walls patterned with mare tributes and posters.
why are horse girls crazy anyway? have we ever figured it out? can we assume that girls who are born rich and given horses are just naturally too spoiled to be sane, or do we assume their brains grow different due to odd activities with said horses