This is a unique situation for Stanford, as Tara always uses all her scholarships, unlike almost every other top program, so there's rarely room for unplanned wrinkles like this. I seriously doubt Tara & Staff would just summarily pick Carrington because she is more likely to be a major contributor, especially given Wilson's history, commitment, and previous failed effort to obtain a waiver.
If I had to guess, if Wilson is fortunate enough to be granted a waiver on her appeal, they will first see if there is a way one of them can be admitted to a co-term or master's program at Stanford that would independently provide financial aid. That would not be sustainable on a four-year basis but I suspect there might be a one-off possibility, as the university's graduate programs are not all need-based aid the way the undergrad is.
The one thing I don't know, but I assume someone around here does, is whether you can use a medical redshirt but then not be an athletic scholarship player? The other alternative, if not, would be to see if either one has another program they are eager to attend instead so everyone gets a happy ending.
Finally, this raises a related question: I know that players seeking a medical redshirt can only play in some relatively small percentage of their teams' games during a season. Is that denominator based on the regular season, or also the post-season? If the latter, does this potentially hurt any players who were injured early in the season and were counting on post-season runs to get them below that percentage?
(Clearly we have plenty of time for this kind of idle speculation now...)