Your Concubine? I'm His Empress Now

Lydia Summers has a scheme, and the piece it is played with is her older half-sister. The sister is Charlotte Summers, who in her first life was the wife of Crown Prince Edward Sterling and spent her strength and her whole store of medical skill on healing his legs. What she got for it was a false charge, a demotion from wife to concubine, and a death in the cold palace. Only as she died did she learn that all of it had been Lydia's doing, and that she had been a pawn from the start. She wakes five years earlier, and this time she means to be nobody's stepping stone. She saves the life of Duke Richard Sterling and uses his standing to build up her own, and from there she goes after the people who ruined her one step at a time. Richard keeps her safe through all of it.