J2 dependent - need work authorization for job in Canada?

I'm a J1 scholar living and working in US with my wife (J2 dependent). Have been filing US taxes as nonresident and paying Canadian taxes since we intend to return to Canada in a few years. In 2007 and 2008 we were living in US but had only Canadian source income, so were nonresident aliens for tax purposes in US, deemed factual residents in Canada, and both paid Canadian taxes only on our income. 2009 is my third calendar year in the US and I just discovered this means we are both considered US residents for tax purposes for 2009 tax year.

From January 2009 onwards I now have only US source income (switched jobs), my partner (J2 visa) lives with me in the US but continues to work remotely at her job in Canada, she has no US source income. But I'm concerned with our change of tax residency that this counts as 'working in the US'. Is this situation something that requires her to obtain a US work permit (which is easy to do for a J2, but which we haven't done because she was working at her job in Canada, paid in Canada, etc.)? If so, how do we go about doing this given that we'd need the work permit for work she already did in 2009 (not knowing we were considered US tax residents until a few days ago due to misinformation from IRS)? She has been paid in Canada for work done in Canada, pays Canadian CPP and taxes, etc.