Complex sentence: Her faux mother-in-law, with a bad heart, tries to claim guilt for the killing in a note she wrote while dying, but the murderer is revealed to be another girlfriend of the blackmailer.
Split into simpler sentences: Her faux mother-in-law, who has a bad heart, tries to claim guilt for the killing in a note she wrote while dying. However, the murderer is revealed to be another girlfriend of the blackmailer.