I agree with Hair and Ing. Hissy fit because she was leaving the barn without a buddy. Dude string horses are notorious about that. The first horse we bought for me years ago was a dude string horse. I had trouble with her in the same way. I got rid of her. It was too much for me to handle at that stage of my riding career.
Becky
Fraid so, too. If I had been packing today she would already be a gonner.
You might could try getting her barn buddy out first. Then saddle and mount them both at the same time. Another trick I used was to load my horse into the trailer and take him/her somewhere else to ride. Usually on a trail ride with Frog and friends. Since we rode in so many different places, the horses never had an idea of just where home was. They are then dependent on you to get them back to the trailer and home. : )