Why is Catherine’s death significant in Wuthering Heights? How is this seen as an escape from her suffering?

During her life, Catherine Earnshaw suffers because of her brother’s sadistic mistreatment of Heathcliff, her increasingly loveless marriage to Edgar Linton, and her love for Heathcliff. Because of the social conventions and legal restrictions of the time, there was no possibility of her and Heathcliff having a conventional relationship, such as marriage. Her apparent endorsement of that fact causes Heathcliff to leave. When he returns from a long absence, having become rich in the meantime, Catherine foolishly believes that he and Edgar might get along. Instead, they argue constantly and, to make matters worse, Heathcliff elopes with Isabella, Edgar’s sister. Once she faces the depth of the men’s animosity, Catherine suffers some sort of nervous breakdown. Combined with her pregnancy, the emotional strain sends her into a deep decline. Shortly after her daughter, Catherine, is born, the mother dies. Catherine’s death is not a complete release, however, because her spirit haunts the heath. Heathcliff's attitude turns blacker than ever as he blames Edgar. As the novel opens, during his initial visit, Lockwood has nightmares of hearing her plaintive calls. After Heathcliff dies, she continues her haunting but now Heathcliff’s spirit and hers are joined.