I think there is definitely a sense in which this novel deals with failures in relationships. Of course, centrally, the novel deals with inter-racial relationships and the various failures that they represent. Note how the novel begins with the newly freed slaves and former slaveowners hoping to receive some form of compensation from the British government. Such a context points towards the very delicate nature between blacks and whites in the West Indies. This conflict literally engulfs the plantation house in Coulibri, which of course symbolises white mastery and oppression, and likewise the newly arrived English colonists in the form of the Rochesters are profoundly prejudiced against blacks. Note the way in which Antoinette is told she must disown her black relatives.
Likewise failed relationships are shown through the irrational fears of miscegenation. Insanity is thought to be a product of Antoinette's relationship with her black cousin just as Annette Cosway's relationship with a black man is the mark of her madness. It is highly significant that in a dream at the end of the novel, Antoinette conjures up a society which is characterised by peace between blacks and whites, signifying just how prominent failed relationships because of racial discrimination is a major theme in the novel.