'd switch barns if there are so many problems why stay and put up with it? Take other people with maybe she'll realize she actually has to do her job. I find it odd that she does'nt have time to muck her own stalls or feed the horses and HER animals but has time to turn out a horse that doesn't need to be turned out. If you don't switch then try putting a note on the door of your horses stall saying "NO TURNOUT!" in big bright letters
Equestrianism; 10% luck, 20% skill, 15% concentrated power of will, 5% pleasure, 50% pain and 100% reason to remember you're absolutely insane to be riding a beast that big.