Olivia's symbolic parents
Olivia is half terrible master and half slave. Her father is a plantation owner who slept with his slave and she became pregnant. He represents the psychic effects of misogyny and patriarchy, the way she feels pressured to do what is lucrative, the way she is made to feel that marriage is her only option in life—these are the effects of patriarchy. And when Dido takes her home to Jamaica, Olivia sees her "mother" figure in action—she learns to love her identity as a black woman.
Dido as a Christ character
Dido is a servant who helps take Olivia from her devastation (following the news that her husband was already married to someone else) to her new home in Jamaica, where she tells us they will be working with Olivia to restore her mind from the damage that her broken society caused. Because she is a servant, and a mother to Olivia when Olivia is in need, and because she brings Olivia toward a new identity and a new life, this would be an instance of a literary device called a "Christ character," where a character seems clearly modeled after the idea of a Messiah or savior.
The anti-husband
If the black women in the story are like saviors to Olivia, then Augustus is the power who betrays her. Unlike the care of her true family, Dido, Augustus stays true to his name, using power and manipulation to make Olivia feel love for him, to make her feel weak, and to trick her into a relationship—after all, he is already married to someone else and has lied to her about it.
The threshold
When Olivia encounters the border of Wales, she has to make a decision. If she is leaving Britain, where will she go? Who will she become? All the places she knows are riddled with sexism and racism, so where should she travel to be at home, to be accepted as she is? The answer is that she must cross the border into a new fate. Therefore, the border scene can be taken as her accepting the call to adventure in the efforts of rebuilding her psyche from the misogyny of her marriage.
Jamaica
Jamaica represents a kind of euphoric reward for Olivia's long life of struggle. She toiled for life and found it, and her reward is literally (Dido tells us this) the restoration of her consciousness. Her mind is healed from the shame that she is subjected to throughout her mistreatment as a half-black woman in America, and then in England. In Jamaica, she matters for who she is, and she is in community with people who don't think less of her because of her race.
