You haven't gained her trust if you haven't gotten her respect at ALL times. They are one and the same to a horse.
NATURAL HORSEMANSHIP does not mean that you have to use mental telepathy or some 'magical, mystical bond' to get a horse to respect you and do everything you ask. It simply means you use methods that the horse understands.
So, in order for you to get this horse's respect, you are going to HAVE TO make this horse understand that it has to go forward EVERY time you ask it to. As a matter of fact, it would not stop going forward when IT wants to. It would not 'stall out', ever. When you have to constantly 'urge' or 'nag' a horse to go forward, it does not respect you very much.
When we sell a trail horse, we tell people not to point it off a cliff unless they are wearing a parachute. This, of course, is just a figure of speech, but it reiterates that the horse will go anywhere you ask it. That means that the horse will hop off of a 4 foot drop into running water -- because we do that on all of them -- without a horse in front of them. They load in a trailer they have never seen before in the middle of the night -- done that, too.
You need to get a pair of long, heavy harness leather western reins. Then, the next time your horse stalls out, you need to spank it good with an 'over and under' motion and MAKE it go forward -- right then and there. A couple of good spankings and it will soon quit stalling out and will take you seriously -- which it obviously does not do now. [You use the 'over and under' motion because it spanks them on both sides and prevents them from spinning to the left when you spank them on the right or visa versa.] When you are through and the horse is going forward freely, you then take the long reins and swing them around to quell any fear that horse might develop to the swinging reins. Very quickly, the horse learns that the stalling out caused the spanking and not the reins themselves.
THIS IS NATURAL HORSEMANSHIP!!! Horses understand this action perfectly. It is exactly what another horse would do only the other horse would use its teeth. If the horse is dumb enough to just stand there and not move quickly enough when a lead horse pins it ears and shakes its head toward it, it would get a large hunk of its arse removed. I know this to be true because I have watched it happen a thousand times. The offending horse will have hunks removed and will have teeth marks that take a week or longer to heal. THIS IS natural horsemanship. It is making a horse understand who is the boss -- who is in charge -- who they need to listen to -- who is the leader. It tells them that when you say "Go!" they need to do just that and not stand around and argue or defy you -- like your horse is doing now.