Simpson and Cook, a comedian, reportedly were seen in New York whispering in each others ears, and Cook "kept coming back to her every time he was pulled away," reported TMZ.com.
However, Simpson ended up leaving the party with hairdresser, Ken Paves, the report stated.
Two nights before Simpson was seen in Los Angeles with musician Mayer, TMZ.com reported.
Simpson has also said that she is glad that her body was not the focus point of "Employee of the Month."
"Thank God I didn't have to wear a bikini for this one and I'm just a normal, all-American, strait-laced, midwestern girl. I need to do that for myself," she said.