Who is Margaret Finneran from The Egyptologist and what is their importance?

Margaret Finneran is Ralph's fiancée and daughter of an investor in Ralph's expedition, CCF. Margaret's feelings for Ralph swing from fondness to hatred as the Australian detective, Harold Ferrell, tells her how Ralph only wants her father's money and that he is probably a murderer. Margaret's weakness for opium and alcohol keeps her in a sedated state much of the time, but while awake and active, she plays with Ferrell's attraction to her.