Shame that really is terrible. What she thinks of humans really is so in her mind and of course every time she is ill, that is exactly what happens and so it re-inforces her to stay away from them
I don't know what to suggest other than the usual for colic which 90% of the time is stress related. So check that she has access to plenty of fresh water (ie humans or other horses are not standing near it stopping her from approaching and drinking when she wants), plenty of fresh fodder (by this I mean a good supply of hay all the time). This means she doesn't have empty times in her stomach to allow build up of acid and that she is not bolting down any "hard' feed. Is it possible she has teeth issues (this will also cause her to not chew properly).
Eliminate all stress. Move her somewhere safe away from human activity where she can actually relax for part of the day WITH her buddies/buddy.
Unfortunately offspring of nervous mares are generally imprinted with this nervousness as they learn it from day one from their mothers who won't allow access by the human. So if you can find a friendly horse or mule to put with her who doesn't react to human presence she will watch and become less so. In my experience (and we often had very stressed people hating horses dropped off) we would leave the horse to the herd for a few months before attempting any kind of interaction. The moving away would become less over time (human presence coming and going with food and water and not attempting to interact). If you really need to do something stressful like they already did, I would always sedate the horse so it's less traumatic (but of course that does cost more!!!). Most horses like this can be rehabilitated eventually but nearly always end up with one or two issues you may not be able to solve. Over time and with some thinking out of the box there is normally a way around it. One horse we had would NEVER give you his back legs (he was rescued with his brother having been found at 3 in a chicken coop!!!). He would never let you approach at liberty (I could after 4 years of trust), so had to be caught when in his paddock and he was ridden up the mountain at least once a week to keep his back feet trimmed). He is still alive today and in his late 20's. Another horse had the same head holding/twitching overkill and came from the spca. As long as she was never tied to anything she was fine.
So she is young and can be helped. Some things may stay with her forever but that doesn't mean she won't ever trust humans for other stuff. Keep doing what you are doing, being there and talking softly and offering something on her terms.