The smartest thing he can he is to dump her, before she does it first, and trust me, she will. Once he stops providing her with leeched fame, easy money and him helping her to stay in America (she is a Canadian citizen).
Anisa will only stay long term with idubbbz if she has no other choice.
However, the second smartest thing idubbbz can do is not to address it. At best, he might do some self deprecating humor in his next video and call himself a SIMP and attempt to make it a meme like his fans calling him gay r*etard. But I doubt he will respond it directly, I think he is smart to know that would 100% backfire on him.