I guess bodyguard is her only one savior who reminded her innoncent but still hopeless when no one in the palace cared in fire so that she survived and met Dowun. Their relationship is like princess and knight.
Then Dowun, he is her next real savior who taught her know how to survive in the palace. On the other hand, she knew he also used her as a tool and that is why she still hold his ring when nervous to remind her emotional childhood who once wore this ring happily before she found out it's not lovey-dovey. As I guess, she is waiting for mutual feeling, the day they can both wear rings?
However, the name she bloomed by cloud, by quite dark yandere Dowun, started getting jealous and would like to get rid of bodyguard. I believe that reaching to the highest position and power for whatever for his family is not only the reason. There must be more to stimulate his behavior and that must convince readers to understand him afterward, otherwise, he's just simple villain who is greedy in power that became male lead.