It would seem so. Mirai and Ashley have both won short programs this GP season, but Nagasu did it with a much higher score. So far, she is the only American to have scored above 60 in the SP in a GP event.
IMO, IF Mirai skates perfectly she will be going to Vancouver for sure and probably be the American champ. Same thing for Czisny although she will probably have to amazing for the judges to give her the benefit of the doubt this time.
However, Ashley and Rachael are so much more consistent it's hard to imagine that one or both of them will not end up prevailing.