I have/had one of those horses! I learned to tie well!
So, I use a neck strap. Clip the lead onto the ring of the neck strap, run the lead end through the throat latch and then the bottom ring of the halter. Tie to something big and strong with nothing else around that the horse can hit. The side of the barn is ok only IF you have something very solid to tie to -- a grade 5 eyebolt right through 6 inches of solid wood (eg. log wall, like my barn); a large enough hardwood tree with no low branches (minimum 10" diameter I'd say -- for something like a maple or oak tree); a 8" square post sunk 4 feet into solid ground or cement. If you can move it with a pick-up truck, it's not strong enough. Tie reasonably short -- 18" maximum, I'd say... guestimating here. I'd have to go out and tie and actually measure it. The idea is that it's long enough the horse can relax when ready, but not so long that (s)he can get a front leg over it, or the head under it.
Let her fight it out. Honestly, they figure it out pretty quick if they can or can't break free. If they figure out they can pull and get free, they will do it again and again.
Edited to add: if the lead snapped, use nylon rope for tying and good solid snaps. I learned about the snaps when my mare broke the snap. The weakest link in the chain...
I did this with my 17.3 mare. She fought for about 5 minutes maybe (seemed like waaaaay longer though), then just tested it out every once in a while. I let her stand there for over an hour. From then on, EVERY time I tied her, ANYWHERE (except cross ties), she had the neck strap on. Thank goodness too because months later, something stupid spooked her when tied. She pulled so hard she brought her back end under her like a reining horse. I told her to "stand". Took twice for the command to get her attention and then she did, with an expression like, "Oh. Ok. Ya, what was I freaking out about again?"
You may have more issues than just tying though. Does she usually yield to pressure in other situations? I know my mare didn't and I had to teach her that as well.