As said before, some good advice has been given. I do not have too much to say without reiteration.
I do not want to jerk her halter or slap her or make her scared of me. I don’t want her to get head shy or jittery.
I will say, however, in a time as such, when a horse is ignoring and nearly dragging you, you need to make your presence known, be it with a jerk or a slap. You will not out-pull a horse. If you try, the horse will lean and drag you, like now.
It sounds like, to me, you are a passive and inexperienced - with and inexperienced horse. That is not a good combination, especially when the horse is doing dangerous behaviors. "Green on green equals black and blue" as they say.
For disciplinary reasons, you can jerk or slap the horse and horse will not be scared of you, given correct timing and it was not excessive force.
If a horse is trying to bite you and you slap them immediately, the horse will not be scared of you. However, if a horse tries to bite you and you wait, even just five to ten seconds, and then slap the horse, the horse will not understand and may startle due to bad timing. Your window has closed. Horses live in the moment. Discipline must be swift.
If my mare tried to take a step out of the wash stall, which she knows not to do and is generally very good about it, and I hit her in the face, on her chest, or even yelled, even if done immediately, she would probably startle given, had I just said the words "back", she would have backed. That would be one example of excessive force.
Also, as controversial as it is, I have hit horses in the face. No, I do not like it. No, it is not ideal. No, I do not do it often.
One horse, a known biter, had ears pinned, neck stretched, and teeth bared - ready to bite. I hit them, hard
, in the face. However, get this, the horse did not become head shy
. Why? Because the timing and force was correct. Also, guess what, they never tried to bite me again.