Who is Elizabeth and Betsey Parris from I, Tituba, Black Witch of Salem and what is their importance?

Elizabeth is Samuel's vulnerable wife, Betsey his sickly troubled daughter. Both become friendly with Tituba on the voyage from Barbados to America, both benefit from her healing abilities and her capacity for compassion, both turn on her when faced with Samuel's power and Abigail's lies, and both (according to Elizabeth) eventually repent. They can be seen as metaphorically embodying what the narrative suggests is the essential corruptibility of the Christian faith and those who practice it.