Describe symbolism in Among Others by Jo Walton?

One main symbol in the novel are the earrings given to Morwenna by the three witches. The earrings are symbolic of danger and oppression, as the witches give these gifts with the intent of stiffling Morwenna's ability to do magic. Unfortunately for the witches, Morwenna refuses to have her ears pierced, thus, thwarting their plan.