In the prologue of "The Canterbury Tales" the prioress was described as someone who is trying to portray somebody else or to project a certain image of what a prioress should be.
The prioress is trying very hard to be dainty and act in a certain manner as a nun but her behavior shows her to be the opposite of dainty. In fact, it would seem that she is a large woman and a vain one at that. Instead of having rosary beads with the crucifix at the end, she wears vanity beads that has a pendant that most likely symbolizes her love for material things.