I've also been wondering whether it was her. I'd hoped it was, because that would mean she was alive then and might be found soon. But apparently she hasn't been seen since.
I gather that there are some brush fires not far from that area. The Creek Fire, which has grown to 45,000 acres, is south of the area where Sandra's car was found and where she was allegedly seen. While I don't think there are evacuation orders yet for either of those places, nearby areas are being evacuated. Also, the air quality is bad.
Creek Fire Information - InciWeb the Incident Information System
(There are a couple of much smaller fires up in Yosemite to the northeast, but those seem to be less of an issue.)
If she's still up there, I hope the fire threat and poor air quality leads her to make her way to more populated areas where she can be seen and found.
Massive evacuation orders posted on the Madrera Sheriff page.
JMO