Why is Constance the most disturbing character?

Constance is Merricat’s 28-year-old sister, who was 22 at the time of the murders. She is widely believed to have poisoned her family despite her acquittal. Constance, however, remains a recluse,who only goes as far outside as the garden. She takes care of both Merricat and Uncle Julian and runs the household, seeming to enjoy cooking and cleaning. Although, Constance knows that Merricat is the true murderer, she allows herself to be put on trial without exposing Merricat, demonstrating her love for her sister. As the novel progresses, Constance begins to doubt whether it’s truly best for her to remain isolated, but after the fire towards the end of the novel, she fully recommits to living in isolation with Merricat. It is important to note that by the end of the novel, Constance is no longer afraid.... she is feared.