You're more likely to see the theme of love treated in Wide Sargasso Sea under one of its many associated emotions: desire, lust, trust, and happiness, but also hate, fear, and jealousy. Romantic love in the novel is constantly thwarted by all the baggage the characters bring into their relationship, including their past histories and their ideas about race, gender, and class. Antoinette is not necessarily exempt from the same kind of racism that marks Rochester's attitude toward herself and Amélie, as her relationship with Sandi Cosway shows. (For a longer discussion of death as a metaphor for sexuality, see "Mortality.")
For Rochester, neither Antoinette nor Amélie are worthy of romantic love because of their racial status; instead, they are objects to be owned and enjoyed sexually.
In the novel, marriage is often a financial transaction that deprives women of economic and political power; only women who can work outside marital boundaries such as Christophine, Amélie, and Aunt Cora can assert some control over their own lives.