I am certainly no expert especially on labs but when I had my lab pup she did that after about three to four weeks of being with us. She just stopped coming to me. I didnt do anything and I dont recall any one thing that could have frightened her..
She would turn around and walk the other way when I called her
Not sure if it was part of the establishing domiance issues or not but was told that it was probably part of it. They go through so many changes at that age.
I tried offering her a treat and putting her on a long lead and calling her to me and giving it to her. It did help somewhat. I got some good advice on here.