The plot is so childish (⊙…⊙ )

Well the fmc is kind of a pushover. How can you trust some stranger wholeheartedly in your first meeting and that stranger is your rival (well we know they aren't even worthy). Sometimes her actions are smart (not practically genius level but she can read the mood) but sometimes she acts completely dumb (￣∇￣"). These are some actions I want the author to clarify.