It takes at least six hours for an airliner to cross the United States coast to coast. Going west, the time zones are in Leslie's favor. If she takes off from JFK Airport at 11 a.m. Eastern time, she will at the soonest reach Seattle-Tacoma Airport at 5 p.m. Eastern time (and that's if her flight has no other landings enroute), but this will be only 2 p.m. Pacific time.
Since Leslie goes jogging and does something with Scott on Saturday before even going TO the airport in New York, and since she will experience the long security delays IN the airport terminal, I don't think it's possible for her to be airborne sooner than the time I suggested here. Maybe, though planning to surprise Tanya, Leslie should e-mail Tanya's parents before Saturday, telling THEM that she will come but asking them to keep it a surprise for Tanya.