Depends greatly on the type of car and its market value where you are, but in general, yes. Sell her there and buy a different one when you make it to Canada.
Also take into account that you must convert the car displays from the nearly obsolete miles/fahrenheit system to metric, it'd probably not be worth it to import the average used car to Canada at this point.
Besides, the current (as of April 2016) weakened Canadian dollar may mean that whatever you get for it in USD can get you at least the same, but often a better car across the border.
