What is the significance of the Biblical allusion casting your pearls before swine? (scene 10)

Blanche uses this allusion to describe what she sees as her own actions. Blanche sees herself as generous.... and though she is monetarily poor, she is rich in spirit.... her mind beautiful. It is also in this section that she continues to delude herself about Shep Huntleigh, who is an illusion in her own mind, all while alluding to Stanley as a pig.