I'm sure they know they are favorites and that they are very likely to make the team but, you still have to show up. As good as both of them are, an inspired performance could beat them especially if they make a lot of errors.
Of course they are under pressure. Just ask Ashley who was a favorite to make the team in 2010 after making the GPF the month before Nationals but one mistake basically destroyed her hopes. And Gracie can't afford another terrible SP like last season at Nationals or it might be all over for her too. They still have to skate well and land jumps. Easier said then done when everything is riding on it.