I think she had an accident and drove either into a body of water or a ditch. Perhaps she did get disoriented while driving. I hate that idea, but seems to fit the complete disappearance.
Replying to myself, because I wanted to add, that while the timeline might fit with when Valerie went missing and where her car was last seen, this UID does appear older, lacks a widows peak like Valerie appears to have and Valarie's nose seems a bit more pert than the UID. I can't tell if the UID has a mole over her lip like Valerie does either. They both appear to have a few tiny moles on their forehead, cheeks and nose but I'm not sure how they match up to each other. I am not sure it's a good match, now with a six hundred sixty second look.
