I got my horse March 18 of this year. She had been at her previous barn her entire life (10 years.) Making a transition like this is stressful for the horse. Mine was a WRECK, constantly calling, we couldn't get but maybe 20 feet from the barn without her getting anxious, she didn't eat the first day, etc. My mare is also dominant...is she by chance in heat? Mine was when I brought her over which made her buddy issue much worse. She wouldn't go anywhere without at least one of the other horses that week. She was a real mess! We also changed her over to a different feed and hay, but transitioned slowly over the course of a week by mixing the old with the new. I can say that just a couple weeks later she has been increasingly better, but she is kind of buddy sour to a certain extent. Each day it seems as though her security bubble is getting bigger and bigger. We can now get relatively far from the barn (other horses) and she calls once or twice, but then gets right to work and relaxes. Just give your horse time...life changes like this can really do a number on them:)
Also, was she a stall kept horse before? Or had she had turn out time? Mine had been stall kept so being turned out 24/7 (only in 2x a day for feeding and if the weather is bad) was overwhelming at first.
Best of luck!