You could start with basic obedience work, things like heel and sit and stay, then visit someone with horses and make your dog practice obedience there. Keep her under control, and don't let her have the "fun" of biting and barking at them, and she can gradually learn to behave around horses.My dog really has a problem with horses, she tries to bite them and barks at them and I'm going to get a horse in the future and I'm wondering how to train her out of it.
For when you get a horse, maybe take her to meet the horse a few times before you bring it home, and insist she behave politely the whole time. Then keep her on a leash or inside some kind of fence so she cannot chase and bother the horse when you do bring it home-- basically, make it clear to her that she must behave around THIS horse in particular.
I expect she will settle down when the horse is no longer new and exciting, as long as you can get through those first days and weeks without her forming more bad habits or anyone getting hurt (dog, horse, or person!)