I finished We Have Always Lived in the Castle. I LOVED IT! I'm so glad I chose it in my quest to read more books. I've been scrolling through Reddit discussions.
SPOILERS AHEAD
I know some people interpret Constance as being afraid of Merricat, but I don't think that's the case. I think Merricat is the only one Constance, the agoraphobic, isn't afraid of. I think in some way, she can see WHY Merricat poisoned their family members (there is clear abuse subtext to me). I've heard some say it's also likely that Merricat was spoiled and indulged, citing the fantasy about her being loved and never punished, but I strongly disagree with that. I think that's indicative of what Merricat wanted rather than what happened.
A good piece of evidence for Merricat and Constance being abused is that Constance is incredibly meek and very much a Stepford smiler. She is ALWAYS doing household chores such as cooking and cleaning. Merricat claims she only reads about cooking in the first chapter. Why does Constance act like the ideal housewife if they're spoiled?
Also, Merricat seems wary of Charles from the get-go because he looks like their father. And when the villagers ransack their home, the imagery invoked is that of violation. I think the clear abuse subtext is made even more so by the heavy implications that their father not only abused his daughters but financially abused his brother as well.
Uncle Julian (who survived the poisoning and was disabled as a result, often refers to his brother as not being generous). Julian constantly claims that they'd try not to eat so much in his brother's house. And Uncle Julian is in many ways framed as a "failed patriarch." Before the poisoning, he failed to provide for his household and had to move in with his brother. After the poisoning, he is dependent on Constance for his basic needs, and he often laments about the loss of his physical health and strength.
I really loved when Constance would say "Silly, Merricat." I just found it funny. I love the ambience of being stuck in time, like a bug in amber, because they refuse to move on from the traumatic events that happened in the house. I love how living characters are referred to as ghosts by different characters. Uncle Julian seems to think Merricat is dead. That she died at the orphanage she was sent when she was 12 during Constance's trial. Merricat thinks Charles is a ghost and a demon that she must ward off. Charles looks A LOT like her father. And in the end, it is Merricat and Constance who end up living at the ruined house, their domain further reduced, haunting the place like ghosts.