Try a knotted halter. They quickly learn to listen to them. I don't like to yank as it causes the horse to feel trapped and they are more likely to rear or do something stupid to escape. With a steady pull they learn to step forward for release of the pressure. Why do I get the sense that she is uncomfortable in this barn? Try the opposite of how you do things with her. Eg. If you tie her in the aisle, tie her facing the opposite way. Do you tie at one end of the barn or farther down? If near box stalls, we know another horse can't grab at her but she doesn't know that so if a stalled horse pins it's ears, she wants to get out of it's way, something you may not have seen.