She did not even have a proof at that time. Not a great girlfriend material imo. I can imagine a situation that she cheat on me, because she thought that I cheated on her.
It seems like there's a hell of a lot of people like that, but being male, I notice it more among women. In particular the habit if getting angry at their BFs/husbands because the men cheated - in
their dreams. Somebody punishing me for shit they dreamed about? End of relationship. They need to finish growing up and separating fantasy from reality.
To be fair, Sage was right - Chad was cheating, it just wasn't another woman. Until breaking it off with him, however, she's just as guilty on the infidelity scale, which effectively means every main LI has been unfaithful to their partners (unless my suspicion about James being imaginary is correct).
That would mean the Others choices are arguably superior from an ethical (albeit immoral) stance. Cam, Rio, Nicole, etc. All single, no emotional betrayal. Not all of them, obviously, but a good portion.