So potions just makes you confident not forcing feelings on anyone thats good

Yea, but apparently she's so retarded she can't get it.

Only sister and ml knows truth about potion
both ex fiancée and jurim just know that he was influenced by love potion not how that really works

No no no. He explained that to her. And he told her that he has always liked her. The author is just making her insanly stubborn for a girl that is supposed to be in love.