Can someone get deported for infidelity if they're already citizens or not?

My older brother got cheated on by his Latina wife after 12 years of marriage. Obviously it's one of the worst experience for him. There are 2 children in the picture, a 10 year-old girl and 7 year-old boy.

She's has already been a citizen (through him) for the longest though. But can she still get deported for cheating on him or not? She's not really remorseful at all, will leave him for the other man and said the infidelity has nothing to do with her citizenship status and he can't do anything.

Can someone get deported for infidelity if they're already citizens or not?
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