I disagree with your take because it's equating an unresolved plot point with "letting a man off the hook".
You're putting a too quick, knee-jerk, unfair expectation on a character, Keeley, for not thinking clearly and misjudging the situation. You're insisting her choices be infallible.
I know you're saying you actually blame the writers, but the plotline isn't finished. We don't have any real resolution yet on if Nate is "let off the hook". In fact, the progression of events, with us soon after finding out other inappropriate things Nate has done, suggests the exact opposite. T