If she was my horse, I'd contact Dr. Valentine and ask if the head tilting is stemming from EPSM , if she has ever seen it. If yes, I would not postpone the proper diet. Period. It can take up to six months until the effect of the diet is visible.
I would not give her bute until I'd have a definite diagnosis on her neck.
Take everything with a grain of salt, I said "if she was my horse". But she has had enough stuff done to her which wasn't necessary at all and didn't heal anything either.
If my horse was diagnosed with EPSM, I'd have it on the proper diet and 24/7 turnout within hours. I would not experiment with any symptom treatments until I was sure the diet is fully working.
This is due to the fact that, in my 45 years with horses, I've seen my share of clueless vets who, and that's the bad part, are not capable of admitting that they're clueless.