I have no idea where she lives or which direction she would have needed to travel from the bingo hall to get there, but I am from the DFW Metroplex and can shine a little light on that area as well as what it would have taken for her to get to that license plate reader on I-35 in Denton.
Watauga is a small and very non-descript middle class suburb in the western part of the Dallas-Fort Worth Metroplex, just east/northeast of Fort Worth. It’s not a bad town by any means, but there is nothing noteworthy about it whatsoever. So unless you live there or have friends/relatives there, you would never have a reason to go there or even remember that it exists, actually. I don’t mean that to be critical or harsh in any way, and there are certainly plenty of wonderful people who live and work there. It just isn’t noted for anything good OR bad. It’s not a high crime city at all, but it wouldn’t rank among DFW’s safest either. So while it doesn’t have any infamously rough parts you need to avoid, it’s like most cities in America where someone out at night, especially an older woman, would need to keep aware of her surroundings.
As far as Interstate 35, it is only a few miles west of Watauga. It runs north and south, with it running through downtown Fort Worth just south of Watauga and then up through a few smaller cities like Blue Mound and Justin before coming into the city of Denton (home to the University of North Texas). If you were to continue north on I-35 through Denton, you would arrive at the Texas-Oklahoma border in around 30-40 minutes, with not a whole heck of a lot in between Denton and Oklahoma.
The sighting of her car on I-35 headed toward Oklahoma at 5:30 am after she just won some sort of cash jackpot at bingo really does not bode well, I’m afraid. I can’t see any reason why an almost 70 year old woman would stay out all night and then drive that far away from her home (going in the wrong direction from her home city) at 5:30 am. However, I guess the dementia angle does offer some hope. It’s possible she got confused and turned around and then drove in the wrong direction for a long time. But that’s still a lot of hours for her to be unaccounted for between when she left the bingo hall and when her car was spotted 30 minutes away in Denton. Where did she go for all of those hours? It would seem likely if she were driving for all of those hours that her car would have run out of gas. Did she stop off and fill up somewhere?
It just doesn’t seem like she would drive herself that far away from home in the overnight hours, and sadly it seems her family agrees. Plus you would think that by now either she or her vehicle would have been located had she just wandered away or gotten into an accident somewhere (even a remote location). There just aren’t any major rivers or bridges or thick woods anywhere between Denton and Oklahoma where her car could have ended up. There is the Red River on the Texas-Oklahoma border, but I’ve driven over that many times and, unlike with other river crossings in the US, that just isn’t a very likely spot for a car to plunge into the river. It would take a lot more than a simple swerving out of your lane to make it from the highway into the river there.
Sadly I think the likelier scenario is that she was targeted and followed by a very bad person (or people) who saw an elderly woman flush with cash. It could have even been someone who showed up at that bingo hall that night for the specific purpose of robbing whatever individual won big.