I've spoken about this somewhat before, but mostly just got mocked. (And I think that part of the thread got nuked.)
Unfortunately, this is very much going to be a case of "Source: Trust me Bro" as I'm not about to out the person. But I have been told by a reliable source that this IS indeed the reason that Jeannie—and also the rest of that friend group that Kai was in—have all completely blocked Kai and cut her off. It doesn't sound like there was any cheating, but it also doesn't sound as though Henry and Kai particularly waited for the dust to settle either.
As I said, you're all just going to have to trust me on this one. Or don't I guess, I don't really give a shit.