To be honest I think they're heading towards Edmonton. The distance between Vancouver and Seattle is less than 4 hours and there was a 4 hour gap between her posting at the breakfast place and her posting the picture of the road. Also from what I've seen from Google Maps the route between Vancouver and Seattle is quite boring, however the drive between Seattle and Edmonton has you going through a lot of mountains and even a national park. Anusa (which YOU should call her because she said on Twitter straight up that she hated people calling her that back in school) is definitely making Ian's life a living hell for that 15 hour drive though, and there's no way she's taking turns driving either.
I wish I was skilled enough at GeoGuessr to specifically identify where that road sign is, it's too low quality for me to read. The truck however seems to be registered in British Columbia, the car in front also has a BC license plate. Must've between somewhere in the middle of the trip.