The king had another woman (which he only used as a pa**), and also wanted to see if the FL will get jealous (which is the stereotype of every manwha in the past and it ended up backfiring and the FL left instead)

But on the FL part, she went with a dragon who holds feelings for her, even though he kiddnaped her (lol) she liked the life of being in a warm place, except with the king, and as the king finally saw them and almost kill the dragon which name is Sid btw, the FL begged not to kill him which made the ML frustrated thinking "like girl he kidnapped you? Do you hold special feelings or something" to sum it up, and he ended up healing the dragon for the FL sake of wanting it, and they fought again and the ML just grew funny jealous because in the fight she only cared about Sid (who gave her his heart or a dragon heart) she really cared about sid for loving her truly and giving her his heart to save her.

Personally, I think both are entirely satisfying to be jealous since the FL barely reacted on him pretending to love someone else