as far as I have read, the crown prince(the other brother) also starts falling for her too but feels weird about it cause he thinks she's his sister. They went on a boat ride together where he accidentally reveals he's been poisoned cause it starts acting up but of course she already knew from the past. He thinks about killing her to silence her but she uses her medical skills to suppress his poison with a kiss to pass her ki or something. After that, he starts having forbidden feels for her too. As for Gong jue, he goes out to do the building task which takes a few years but before he left, there were more plots to kill or stop him from going. Our MC foils all those plans with her smarts and even the crown prince helps a little since he has a crush on her now. Last part I left off is when she left the Palace to go get Gong jue who is still a huge siscon but doing a good job with the task.