We didn’t find her car, but we did find a BLM campsite host who told us that her car had been there since Thursday–and that some hikers had found her that morning.
Took the Tucson police a couple more hours to get back to us, mostly because there were some county line issues involved. I think I’m glad we found out from the BLM guy instead, though.
And for those who have been wondering and asking elsewhere: the reasons kathlaw gave primarily had to do with finances and concerns over CFS-type health issues, not anything more than that.