I'm guessing, USCIS has a problem here is that they (the friends) live in the US illegally. For anyone that spent over 365 days in the US illegally the penalty is to live outside of the US for 10 years. This is what your friend trying to fight and the odds of her being successful is near 0. Otherwise, Canadians marrying US citizens have a very straightforward path to get to green card and then citizenship (as is with most nationals).