You should stop LOL-ling because it is apparently interfering with your reading comprehension. I'll say it again: it is legal for an alien who has entered the country legally -- which this woman did -- to meet and marry a U.S. citizen and then apply for adjustment of status -- which this couple did.
So this couple did choose to be legal. How many different ways do I have to say it before you understand?
So why is law enforcement involved?