She tried to put both her love interest and her duties on the same level morally, which was an insanely bad decision in the end, because neither won. Vi lost her sister and everything in her life, while Caitlyn became this selfish, almost narcissistic, general who had no allies.
I can understand why she chose to demoralize Vi; it was her job as the sheriff of Zaun who was interrogating a criminal. However, it still made no sense for their progression to some extent. From S1, it was written in the stars that they would go down different paths when they wanted to understand and empathize with each other with a common goat, but S2 almost ruined that because it seemed like Caitlyn never wanted that from the beginning.
At least, that's what I understood.