Mary Lee Harvey is not a known person or term. It appears that the name is a combination of two well-known figures: Lee Harvey Oswald, the assassin of US President John F. Kennedy, and Mary Jo Kopechne, a political strategist who drowned in a car driven by US Senator Ted Kennedy.
There is no evidence to suggest that Mary Lee Harvey is a real person, and it is likely that the name is simply a combination of these two other names.