One Step Forward, 10 Steps Back

Help! We got our first budgie (together, I had one that spent its entire life biting me when I was a teenager) on October 20th. She was a pet store bird but for a pet store bird she was very docile. We let her settle in before beginning to try to interact with her and did everything by the book. Things were going great! I was clicker training her, which she absolutely loved. She interacted with both my fiance and I cooperatively and never bit either of us. She got to the point where she would run back and forth on the bottom of her cage and call for us to get her out. When we came over, she would get on the door as we swung it out and eagerly jumped to our fingers. We went out of town for 4 days over Thanksgiving, and given that I had not had any time to condition her to low stress travel I left her home where a friend (whom she had met and interacted with on numerous occasions) was to check on her and put on the tv for a few hours for her every day. When we got back we came home to 100% a different bird. She no longer wanted to come out or do any of her clicker training games, her only goal was to fly back to her cage or not leave it in the first place. Trying to think of things that may have changed I remembered that we had accidentally changed millet brands since we got back (she only gets millet outside her cage as a reward for coming out). I changed back and she was back to normal for a day; I was so excited to show my fiance who was on a business trip! Then when he got back the next day she was sort of middle ground, more cooperative than she had been lately but not herself. Now a few days later she wants nothing to do with her training games or us, her only goal is to get back to her cage. I am at the end of my rope; I had a keet that I had spent its whole life trying to at least get to a point where I could change the cage without getting bitten and failed. I was so afraid I was going to have another long term commitment that hated me when we got Chiquita but then things started out so well! I just want my friendly, social girl back :sad: