It gets very tricky, i know there is something like foreign tax credit or something like that (she also has to be paying taxes in a foreign country, usually it's more than the US and the US will give you credit for the taxes you pay over there), she has to be outside the US a certain number of days a year, and there are more rules, i would go to the big tax thread. cuz i am not a tax expert, but i have seen some people use this on their taxes.
edit::::answer to question yes she does need to file, and i still say you should put it on the big thread, cuz you should not be listening to me.