I mean I don't see any problems with her clothes, they nice and cute. she does not suppose to be the queen of beauty anyway. the clothes fit very much.
really? I just love it when she calling him father, by the way, I read she is not calling him "her father", it is a problem with the translating. she is calling him a tittle for someone older then her that becomes a father. at least that what I read in the comment section. it makes much more sense now (≧∀≦)
In the original webtoon, she is legit calling her "아빠" or appa. Which just means dad (casually) I don't know if she also calls her "아버지" or more formal father since the king/emperor had a talk with her about it. She calls her your highness in the late chapters but slips "father" when she's not conscious

Every time the mc says father a little piece of me dies
Also I’ve seen a lot of people complain about how young the mc dresses or looks but didn’t the mc just reach adult hood?