The only way for the sister (the villainess) to win is to do this: First hold a very large party with all or most of the nobles from the north and the capital.
Sometime during the party the villaness forced the FL go back to her bedroom, there the villainess maid or someone from the villainess side give the FL poison tea or some sleeping pills to make her go to sleep
During the party the villainess announces to the while party that she is the Duke fiance, meanwhile, someone takes the FL outside and throw her into the woods or something
There the villainess maid (the one that she beat up) "find her" and wake her up and tell her a that she was sleepwalking and that she was "concerned" for her so she followed the FL outside if the FL does not believe her that the maid will tell a sob story and how she want to leave the villainess and live her life. The maid and the FL would the go back inside the mansion
Meanwhile the villainess would say that there is fireworks or a surprise outside to congratulate of her engagement however what would the party member would find if the FL and the maid. (During this the FL would look dirty probably have a ripped dress)
The villainess would act all sympathetic but also insult the FL and how did she end up like this and may suggest the she had a secret meeting with another man.
BUT THEN the maid blurts out that the FL is sleepwalking infront of of everyone
The FL would probably run inside and the Duke will probably go as well
If the villainess fails to get the Duke to make her his fiance that the villainess can spread a rumours across the whole country that the FL stole her fiance was bullying her and a bunch of nasty stuff and basically destroy the FL reputation and IF THAT fails that she can drug the FL again and stage the FL self deletion.
The only way for the sister (the villainess) to win is to do this:
First hold a very large party with all or most of the nobles from the north and the capital.
Sometime during the party the villaness forced the FL go back to her bedroom, there the villainess maid or someone from the villainess side give the FL poison tea or some sleeping pills to make her go to sleep
During the party the villainess announces to the while party that she is the Duke fiance, meanwhile, someone takes the FL outside and throw her into the woods or something
There the villainess maid (the one that she beat up) "find her" and wake her up and tell her a that she was sleepwalking and that she was "concerned" for her so she followed the FL outside if the FL does not believe her that the maid will tell a sob story and how she want to leave the villainess and live her life. The maid and the FL would the go back inside the mansion
Meanwhile the villainess would say that there is fireworks or a surprise outside to congratulate of her engagement however what would the party member would find if the FL and the maid. (During this the FL would look dirty probably have a ripped dress)
The villainess would act all sympathetic but also insult the FL and how did she end up like this and may suggest the she had a secret meeting with another man.
BUT THEN the maid blurts out that the FL is sleepwalking infront of of everyone
The FL would probably run inside and the Duke will probably go as well
If the villainess fails to get the Duke to make her his fiance that the villainess can spread a rumours across the whole country that the FL stole her fiance was bullying her and a bunch of nasty stuff and basically destroy the FL reputation and IF THAT fails that she can drug the FL again and stage the FL self deletion.