you could try global herbs tendoneze and to calm them down I was advised to try argent nit which is a homeopathic remedy you can get it from boots the cehmist or on line you should give 5 tablets a day it worked wonders on my stressy mare when on box rest
How bad are your friends horses hocks ie whats her age history etc. As my mare is a bit stiff behind and Ive had my vet take a loook. Im wondering at what level do these specialists become worth calling in for advice??