When Dana first meets Rufus in Maryland, her reaction to the way he interacts with her is typical of her 1970s self - most of us would've responded the way in response to Rufus's language. He calls her the n-word and tells her to refer to him as master, something she understandably feels incredibly uncomfortable with, given that she's a woman in her 20s and he's a child. She tells him not to call her that and that it's not acceptable, something that Rufus accepts somehow. At least when Rufus is a child from that point onward, they seem to have a healthy relationship where Rufus has some love and respect for Dana and in a way, Dana is able to maintain her idealism.
Rufus soon becomes a man however and society around him makes him aware of the sheer amount of power that he has being a white male slaveowner. Rufus starts to emotionally manipulate Dana and treats her more like his slave than anything by making sure the threat of him selling her away always looms over her head. Rufus however still does have some love for Dana - when he threatens her at gunpoint to make sure she doesn't ride off with Kevin on horseback away from the plantation, he is trying to intimidate her because he has been taught that black women are nothing but property for him (similar to why he buys Alice out of freedom) but there is also some affection in his voice. Rufus does have some level of love for both Dana and Alice but he has to mask that because he is not allowed to love them in the world they exist in. He can rape them and abuse them and have children with them but he cannot have any sort of affection for them. Dana's hopes in his childhood that she can change him and make him not another Tom Weylin seem to have backfired and have made Rufus in ways, worse than Tom Weylin himself. While Weylin was direct about his apathy towards his slaves and they always knew what to expect, Rufus's psyche has been complicated by what Dana has introduced to him, that the kind of behavior he sees everywhere is not okay, and the society around him that reinforces the exact opposite. Rufus is a slavemaster that tries to love, even when the two are contradictory. Rufus tries to love the woman who he bought out of freedom and expects her to reciprocate love when he is essentially raping her and every night is hell for her. We can see Dana starting to accept some of this as well. Part of this because she too has some stake in this story - Rufus and Dana's union is the reason why she exists centuries down the line. However, we see her again and again trying to cajole Alice into going to Rufus's room, not giving her many options and at some points, being completely apathetic to Alice's situation. 1970's Dana would've been outraged but after years of being in Maryland, Dana has almost accepted that this is a way of life.
In the last scene of the novel, when Rufus is about to rape Dana, we see her again in her head trying to justify this. He smells good! However, she is finally able to fight this off and stabs Rufus, allowing herself to escape from this nightmare. Can we say Dana has fully succumbed to 19th century values? No. But along with her arm, she lost some of her idealism and naivete in Maryland. The little hope that she had that her family was made out of a loving and consensual relationship is shattered, as does the history of slavery to most who are unfamiliar with its horrors. Except this time, Dana has actually experienced it.
