@Rose You're not looking at the bigger picture here. Just like how everyone thought Susan was the victim simply because of rumors and no concrete proof whatsoever, the same could happen to her. People could just make up some nonsensical rumors that sound pleasing to the jealous audience and if enough influential nobles, who have malicious intent towards ml or fl, repeat them it will basically go viral in the both noble and common society. She can't change her birth status and people who have feelings of envy towards her will also never forget her birth status which will make them look down upon her either consciously or subconsciously. The extravagant proposal will basically send a message conveying that whoever tries to do harm to FL will court severe consequences without fail. And I'm pretty sure not informing ml of the plan is also necessary because it would give him the push he needs to be certain of his feelings and would also make his proposal completely sincere. There are veterans in the nobility that would see through a staged grand declaration of love.