I think there are two clear options for Athing Mu after tonight, either of which could be a good one:
First, this serves as the excuse she's looking for leave running behind and fade into obscurity. Which is fine. She can live a nice, quiet life, and periodically give an inspirational talk or do a lowkey photo shoot to bring it a bit of quick cash. She'd lose any future Nike money, and I don't think she'd make it as a professional model, but she probably already has "enough" anyway, if she lives prudently.
Second, this lights a fire under her ass and makes her realize how much she misses running (and winning). She ditches Kersee, goes back to her old college coach, and returns brighter than ever for 2028.
Obviously, I prefer Option 2. But Option 1 may be the right one for Mu, and if it is, she should take it, with all of our best wishes and thanks for a fantastic 2021. I just don't want to see another year like this one, injured or not, where it's clear that she's anxious, under-trained, and doesn't want to be there.