It's entirely about what you think about mistakes and redemption. Is it cheating in a classic sense? It's close, it's the lead-in to real, tangible cheating. It's a thought of cheating. It's emotional cheating, if you are with the term.

Personally I believe in redemption in the sense that, nothing literally happened, and you can still have faith in this person and try to guide them to do better. What they did was wrong but I wouldn't do anything yet - if a person has cheating tendencies, they'll resurface themselves. I wouldn't wreck their life before something even happens.

But it's really about your morality. It was a bad thing to do, but I don't call it irredeemable. Maybe you do. That's your decision.