Du Yi Kuang Fei

One day, Bai Xiaoxiao finds herself transported back in time into the body of a fat girl? People thought the general's daughter is soft and easy to bully. Well, she'll show them! After a few days, she's seducing pretty boys and fighting off bitchy girls… when the tsundere prince comes calling? What's this about mutual cultivation? Step aside, Mr. Prince, and let me show you what a trained poison expert can do in ancient times!

(Source: Kuaikan, translated)