Ooooh. She's so loverly. Your horse anatomy is so perfect and lovely...I love the muscle details you've included. And of course, I love the mane and tail. Especially the tail - it looks like you captured it in mid-swish or something.
I love drawing muscles - and because of that there is always a risk of exaggerating them... I don't want to make my pretty horse look like a bodybuilder! But I trust you saying the anatomy looks good so hopefully we're still far from the builder look.