Without knowing anything, my guess is that this decision was made in consultation with US Figure Skating. Some skaters seem to do well with back to back events, other don't. Some skaters are injured a lot, others aren't. I know nothing here, could it be that Ava is recovering from an injury and her team doesn't feel that she could get through 2 intense competitions back to back? This schedule is rough. I anticipate seeing a lot of tired skaters at Four Continents. And if any of of them don't think they can do both and stay healthy, they should pull out--of one or the other. Health is more important than my disappointment.
I can't see US Figure Skating being OK with a skater saying, Four Continents is more important so we're just blowing off Nationals. Thanks for the assignment! There has to be more to the story that we're not getting. This is why I suspect a discussion was had and they all agreed that she could pull out of Nationals.
What this means for the rest of the season? No idea.