I think it’s more the lying and conflict of interest. Is it bad to cheat on your spouse? Yes. But I doubt people would care that much or that she would get fired if it was with somebody random and not somebody that she is supposed to objectively report on and/or somebody that could give her an unfair advantage with insider info. Just standard conflict of interest stuff and lying to your employer about it that makes it a firable offense. It’s like a lot of workplaces: it’s not ideal to have workplace romances, but as long as everything is above board, reported to HR, no major power dynamics issues, etc. then it’s usually fine. But if you’re cheating, sneaking, lying, and somebody could be translating that relationship to a workplace benefit, that’s a problem.