Consideration of "bordable" states in a Graph Theory coloring question

There is a question in my Discrete math class homework that is asking me:

You and your friends want to tour the southwest by car. You will visit the nine states below, with the following rather odd rule: you must cross each border between neighboring states exactly once (so, for example, you must cross the Colorado-Utah border exactly once).

All I am a bit confused about is if states that "corner" each other would be considered bordering states. By cornering I mean this:

Would Utah, Colorado, Arizona, and New Mexico all be considered to be bordering states because they are "touching corners? For example, I do know that Utah is neighboring both Arizona and Colorado because it has "edges" that are between them, but would touching corners be considered edges in this way as well?

If the problem statement is not clear enough on what states should be considered as adjacent, then it is ill-defined. Both interpretation could be correct, in the sense that both would give a well-defined graph.

That being said, physically it would not be feasible to go from Colorado to Arizona without partly crossing Utah or New Mexico, as a car is not a point, it has some width. I would consider this to be strong-enough evidence for not considering states with only touching corners to be adjacent.

Also, in the context of planar graphs, the dual graph would not have an edge between two faces touching only at a vertex: the edges of the dual graph are in correspondence with the edges of the planar graph. If the exercise refers to dual graphs, then there is no ambiguity and there should be no edge between Arizona and Colorado.