She's definitely putting everyone at risk by doing this. I would definitely say something before it is too late. I personally have anxiety issues and cars or any vehicle makes it worse. It's very dangerous going that much over the speed limit alone. Maybe try bringing it up when you're not in the car. You don't want her to get upset while she's driving or in front of the kids. Does it scare the kids? If this is causing you anxiety as well you could talk about that too.