Shedding the Pounds, Claiming Her Crown

Cynthia Shaw is a modern secret agent who wakes in the body of an overweight girl in another world. The father of the family has ignored the girl since her mother died. Her fiance breaks off the engagement in front of a crowd, and her scheming sister takes him for herself, then arranges to have Cynthia killed. Cynthia survives, decides she will settle the account, and starts training in secret to change the body she is stuck in. She is out running at night on one of those training sessions when she finds a badly wounded man and gets him out alive. He turns out to be the third prince, the one in line to be named crown prince, and once he recovers he sets about marrying her at any cost. The girl the household despised keeps working her way up, and the court has to reckon with her.