LET'S WIN-WIN's Things

Sorry i only know a specific scene and i believe it revolves around a noble purple haired fl who is engaged to a prince(?). the scene is basically in a blown up room with a huge hole, and happens when the fl “injures” the villainess and her powers go berserk because the ml happens to see the scene in front of him and she’s scared he thinks that she injured the villainess so in the end she falls out of the hole falling into the ocean and ml jumps after her. My memory of the story is not that accurate but I’ve been searching for this manga for 3 hours and i’m desperate.

Okay so i’m trying to find a manhua/manhwa i’ve read but i can’t seem to find it T_T
I believe the FML has red hair and she and the ML have been forced together. One day she falls in love with the white haired knight (slergy(his name is something similar)). However the ML sent slergy to fight in the war (?) and he died. Depressed about her lovers death she vowed whoever the ML falls in love with, she’ll kill them as revenge. Sorry for bad explanation :(