The Oregonian newspaper reported that the alleged unwanted sexual encounter happened in November. The paper said the Democrat told senior aides the encounter was consensual.
The paper reported Facebook notes indicate the woman graduated from high school in 2010.
The woman reportedly decided not to press changes because there were no witnesses and it would have been her word against Wu's.
Pelosi talked with Wu Saturday but did not disclose details of the conversation. Despite calls for his resignation, Wu kept publically silent Sunday.
Wu's only response so far has been a brief statement late Friday: "This is very serious, and I have absolutely no desire to bring unwanted publicity, attention or stress to a young woman and her family."
The Associated Press contributed to this report.