In the church scene Felicia looked like she was possessed and kept chanting the word "whores" it is like she knew what was going on in the Lennox mansion or something. Also Alex knew about Felicia's "medieval morality."
shareI was thinking along the same lines as you. Or maybe that she was potentially a witch also, but repressed her desire to join the other three women out of a sense of morality and/or faithfulness to her husband. So instead, she turned on them as an enemy after her leg was broken.
_________________________________
"I'm sorry, but.." is a self-contained lie.