TL;DR: Clinic doctor was jailed during a revolution for treating soldiers. She was back to being 18 after a witch helped in prison and to being in an orphanage. Instead of owning her own clinic again, she used the medical experience from her past life to become the assistant to the palace doctor. The palace doctor is her father, but that is unknown to both.
A clinic doctor was jailed after/during a revolution against the kingdom she lived in for treating soldiers. She helped an elderly woman in jail, who offered for her to go back in time. She accepted the offer and became eighteen (18) or a bit younger. She was back to the orphanage that she was in before; in her past life, she had plans to become a clinic doctor and did so after leaving the orphanage. This time, she decided to use her medical experience to become the assistant to a palace doctor or something equal to that. She got the job and was the assistant to a man, who had a daughter with a blonde woman, but the woman died after giving birth to the child. He knew little about his daughter, not even her hair color, though he assumed it would be blonde. In reality, the main character is his daughter. There was a moment, where a third character commented, that they (mc and the palace doctor) looked very similar/family with their brown hair. They both replied, that a specific percentage of the world's population has brown hair. They third character commented that they even answered the same way.