In the beginning, the female lead is isekaied to a novel or manga she read and becomes a character that was never in the book. The female lead has a brother who is practicing sword fighting with a knight and his eyes start glowing as he is getting really into it. The female lead is his younger sister and holds his face, telling him to take it easy on the sword fighting; his eyes stop glowing and he smiles. It cut scenes to him and her at two graves which belong to their parents and he is now in charge of the nobility and lives with her. I think the male lead had white hair, but the young female lead also had a bond with a woman who wore a mask outside the house due to an accident and her face was burned. At one point the female lead saved her from herself blowing up at a party. At that same party she was introduced to the original female lead of the story, and found out that she was hired to become her bodyguard by her older brother, who I'm pretty sure was black haired.
I'm trying to remember what it was, but I can't for the life of me.