My Mare did EXACTLY the same thing! she is now 21 8<)
She NEVER did like the girth tightening!
Girths with ELASTIC ON BOTH ENDS are easier to tighten and are more comfortable for the horse!
Fix int to place in the stall and finish to tighten out outside.(like others had posted)
Reinforce positively just befour tightening and just after with a treat, and reprehend if she tried to bit me with a strong HEY, NO.
She eventually did get better, she would not turn around to bite me, But I always had to pay attention not to have anyone to close to her head or she would still bit, 2 seconds after everything was just fine 8<) you could pet her as much as you wanted 8<)
She had NO vet problems 8<) she just did not like it!
Good Luck! Happy New Year!