User blog comment:Theory of everything/Grimm Speculations Part Six: The Grimm Family Tree/@comment-50.90.228.226-20120821095024/@comment-5190036-20120824042526

I think Kelly may have stayed in Portland to make sure that Nick's friends stayed his friends after he no longer had the coins (which confer leadership to those that carry them).

Or maybe she just prefers the short-term mobility of a car, wants to avoid cameras at the train station, and didn't want to upset her policeman son by letting him see her steal a car.