“How did you get that information?” asks Cheater.
A Cheater who responds this way is a Cheater still committed to her sins. She is not repentant. This is a question about how she got exposed. It is about Cheater damage control.
There’s a leak!
The problem isn’t her behavior. For her, the problem is you knowing about it. She no longer has a monopoly on that critical information. So, she asks about your sources.
I do NOT recommend telling!
“I have my sources. How I know isn’t the problem. Your cheating on me is!”