Rachel sounds right on. Have you done introductions with the horses and her yet? Maybe that would help. Ease her into it and at some point she will get used to them... I HOPE! I know exactly the type of behavior you are referring to as well and it is very hard to deal with. The dog is so completely focused on that one thing and no matter what you do, you won't get their attention. Is she around you and the horses when you are grooming or lunging (if you do any of that)? Do the horses seem upset by Patience? If not then you could try letting her near them when you are around the horses and see what happens. You obviously want to be very careful so she doesn't spook the horses and she or you don't get stomped on! But, it might do the trick!

Maybe Patience just has an identity problem and thinks she is an Australian Shepherd or Border Collie !