No doubt she is an opportunist. If there was any publicity re: her fake marriage at the time,they began living together, he either knew the marriage was a fake, or didn't care if it was genuine. As he probably was quite pleased with their cohabitation, he could overlook knowing of her illegal status.
I would think she has a manager who should have looked after her status better. She apparently was cognizant she was illegal, but it appears she could have sought a green card or some other avenue than marriage. But I suspect her career took precedence over everything else.
Another empty-headed beauty who fell prey to an empty-headed photographer, who, I suspect would "make her a star!"