
I did it because document is fake but I can't prove it that is fake ( seriously this is your defense). We have him alive so we can use him, no you can't die ( letting him keep weapon and talking how they will use him in front of him). Where is a father of her? King who is giving documents to translate to some girl knowing that it's his daughter scam but behaving like naive noob when matters of his kingdom are in full blast)

I am just on 13th chapter but solution of her " wearing the same problem is so obvious that it's hurt to read it again and again" Change tailors, change servants or choose outfit for the party in last possible moment so information about it won't leaks. It is obvious that someone is leaking information about you and this is what you should solve first

Don't forget, the bully has money, power, and parents that don't care what she does. She's better off identifying the spies and using them against the bully, especially since any new staff that come in could be sus too, she cannot trust anyone at this point, except her family and fiance. She would be better off cashing in all of her lottery tickets and escaping (on foot) to the mountains as a sheep herder.
She already have money
She already have support of her uncle
She got her mana back
She knows that marriage with Duke can be potential red flag on her surviving
Although it's Duke who should be more in marriage he left all problems to deal with his family to her ( he basically doing nothing or barely minimum)