What Foxhunter said is what I did for Brock when he learned he could break free. Worked a treat, he stopped pulling back no problem. (So he learned to untie himself - ugh.)
But she really sounds like she's getting into right brain mode when she does it, especially if she didn't release and passed out! Whatever it is is causing her to get into flight mode so it might take a while to get her back in the right frame of mind to learn.
But yeah, learn to do a quick release knot as Cherie mentioned, very handy in an emergency.You might want to avoid tying in a rope halter too - I've known nasty head injuries to occur with horses pulling back suddenly. She's clearly not reacting to pain/pressure from the halter so I would avoid using anything that relies on that or she might seriously injure herself.
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