Yes, she might do the mile at Arcadia. But she would need to run faster than 4:31 to even meet the "B" standard for the Olympic Trials. The "A" standard is 4:25. Those are some really fast times for a high school girl.
In any case, it would be interesting to see her try.
Would an en-route time at Arcadia qualify her?
Not sure if Arcadia records times at the 1500. I suppose if Sadie asked them to set it up they probably would.
It would cost the meet director some extra money, but then he could advertise that he tries to help runners get into the Olympic Trials.
But I highly doubt that she would run a 1500 en-route faster than her PR of 4:09.70 in a mile race.