Sue encouraged them, thinking they were shy. Although the instruction periods had started well, attendance gradually dropped and Sue had to discontinue them for lack of attendance. The woman saw the instruction period as a threat to their way of life. In a group situation personal contact tends to be lost. This personal contact is very important and individual instruction is better in the loony run.
Aborigines are shy.
To be singled out in front of a group was embarrassing to all. Most of the women who were chosen to demonstrate were young and had therefore no authority to tell the others what to do. Although possible, this is not very likely in the context of the story. If this was so the instruction periods would most probably have failed much sooner than they did. The story says that there was initial success, indicating that the women were keen to learn.