I had a horse I trained that was like this and some one suggested this to so here's what you need....
-6-8ft of Twine, sturdy twine but easy enough to break if she pulls back to hard.
-A golf ball size ball that has a hole through it like a bead, I bought one from a craft store that was wooden.
-An O shaped tie ring.
Alright once you have these things this is what your going to do,
Take the twine and tie it to your horses halter, take the other end of the twine run it through the tie ring that should be secured to a post or stall wall, and once the twine is through, tie the ball to the end of it. This way when your horse pulls back she has about 6 or 8 ft of pullage and wont spook and may or may not stop pulling back, if your horse doesnt stop pulling the twine will give a tight tug and then snap so no worrying about bent neck. This will take a while so have patience.
Or you could teach her to gound tie but this took my horse 2 months straight to learn. Take and lead your horse to where ever you groom, tack ect... everyday and put the lead on the ground , Say 'STAND' and then start grooming, if your horse even moves one hoof, place it back exactly to where it was and again say stand. This will take a while but once your horse gets it it will be like a dream. My horse stands now with no halter or lead and lets me tack him completely without moving in a 100 acer feild it is much worth it.
Thunder 9yr. black Mustang Appy/Paso
George 18yr. Red roan QH
'Grab life by the reins'