Faye is the owner of the whorehouse that Catherine eventually takes over. Faye is a lonely woman, and Catherine manipulates Faye into thinking of her as a daughter. Faye trusts Catherine, and writes her into her will. When Catherine discovers this, she slowly poisons Faye, successfully killing her and inheriting the business.
The timeline below shows where the character Faye appears in East of Eden. The colored dots and icons indicate which themes are associated with that appearance.
...to execute her plans, with characteristic slowness and patience. She spreads around the news of Faye’s will to everyone in the house, then blames the cook for letting this secret out.... (full context)