At the border they might ask for proof that you still have a "home" in Canada. Other than that, as long as you qualify for the TN visa with an appropriate NAFTA job then you're good to go.
Hi there -
I'm fairly familiar with US immigration as I grew up there as a Canadian citizen.
ANYWAYS - She can enter the country on a B-2 visitors visa. This is good for 6 months upon entry. It is then possible to apply for an extension of 6 more months, however, it is unlikely to be approved...