What is the "mood pillow" in the novel, The Other Alcott?

May first makes the mood pillow in Chapter Three when she and Louisa are living together at Orchard House, their family home. After Louisa dismisses some fans from the house, and in order to get a favor from Louisa, May starts to sew the pillow. May explains to Louisa if she places the pillow at a certain angle, they will know she is in a good mood and can receive visitors and fans. If she places it at another angle they will know she is not in a good mood or as May says “you’re feeling prickly” (26). At the time, May uses it as a bargaining chip to ask Louisa about living with her in Boston while taking art classes.