Complex sentence: Her son died some time before the novel begins and his death leaves a bitterness within her with spurs her to give Skeeter her memoirs and thoughts, to help change the embedded Racism of Mississippi.
Split into simpler sentences: Her son died before the novel begins and his death leaves a bitterness within her which spurs her to recount to Skeeter her memories and thoughts. Their shared intention is to help change the embedded Racism of Mississippi.