This novel was called "The True and False Daughter of the First Prince"(Author: Qi Tian Tian)! The female lead transmigrated to a royal family and became the first daughter of the current Prime Minister. She met the male lead, Prince Nangong Yi, and another male lead, Nangong Xiu. The female protagonist's sister was the imperial concubine's daughter, Wei Guanshu. I hope you like this fairy's recommendation. Muah ~😗