This should be the novel,"It's Not Easy to Be a Stepwife in Time Travel." The female lead was called Su Xizhu, and the four sisters were called Su Mei, Su Lan, Su Zhu, and Su Ju. I would like to recommend this novel to you. It tells the story of Su Xizhu's struggle between her sisters after she transmigrated to ancient times and the difficult situation of becoming a second wife. At the same time, there are also some plots of the struggle in the palace. I hope you like this fairy's recommendation. Muah ~😗