The "original" novel doesn't sound like love at first sight. Rather it sounds more like a depressed man finding someone that closely resembled his dead wife than love at first sight.
I don't get the cliche hangup that's happening here when the MC should have realized that especially after recalling the story. Why does she care about the female lead crap when the only reason he fell for the lady was because he was still in mourning over the loss of wife and child?
I dunno. This plot point seems feels really forced. Like I would get it, if the ML fell for the other lady and started to cheat on his wife and the two cheaters killed her sister instead of divorcing her because the cheaters didn't want to lose the blood nobility thing.