Final answer:
The quote does not pertain to Faunia Farley. She is a character from Philip Roth's 'The Human Stain', and during her affair with the protagonist, she is 34 years old.
Step-by-step explanation:
The question is about the age of the character Faunia Farley during the affair. However, the quote provided 'Three summers since I chose a maid, Too young maybe but more's to do At harvest-time than bide and woo' does not refer to Faunia Farley but seems to be a piece of poetry that discusses the choosing of a helper or a maid who is on the younger side. This excerpt does not provide a factual basis to determine the age of Faunia Farley during the affair. The character, Faunia Farley, is actually from the novel 'The Human Stain' by Philip Roth, in which she is portrayed as a 34-year-old woman during her relationship with the protagonist, Coleman Silk.