"I've always wondered what is it about horses that makes preteen girls turn to mush."
Horses are frequently better looking than pre-teen or teenage boys. Are too, are too! They're big handsome/beautiful animals who rely heavily on human beings for their care. And young women love to take care of them.
Learning to ride well gives young women (anyone, really) the opportunity to feel a sense of mastery and power over an enormous animal. As well as a sense of mastery over one's own self. It's a challenge to be in charge of a 1,000+ pounds of horse flesh. It requires courage, singlemindedness, self reliance, problem-solving, poise, and countless other things a young women might not be called upon to practice in any other arena.
Not to mention how much fun it is to ride. Riding through a field at a full gallop at 11-years-old is as terrific as it is at any other age. Difference being, young women rarely feel as independent and as in charge as they do atop a horse.
I could go on and on but I imagine that will help you understand what isn't even a question for young women. They're big, they're beautiful, they need stuff, they're fun, and they give young women a tremendous sense of independence. That about wraps it up.
Another great thing about horses, it lets girls get the whole "crush" thing out of their system instead of taking it out on boys . ..
Horses kept me out of trouble all the way through high school.
Great post.