You should never watch any historic drama (Korean or western) with a 21st century mindset.
A court lady is just a servant and she is treated like one. In fact she’s quite privileged because she lives in Palace.
Just imagine it’s a modern drama with a chaebol and a candy. Nothing is invented, it’s always been there.
As for episode 5 scene, as fas as I know, Deok Im place was changed son Yi San mother could talk to him about not having a court lady as a concubine, and Yi San said he would never do it because they are low rank commoners and not fit to him , and Deok Im heard it.

Social conventions of the palace dictate that she apologise thus.
If a personage of lower rank, particularly a servant, to a royal, misspeaks, they must apologise, or they risk death essentially. There are formalities in address and speaking and language that they had back then, which we do not have in the same way now. Even modern Korean, which still is a formalised language (jondaemal and banmal), was even more so historically, particularly in the palace, or from royal/noble to commoner/servant/slave.
It can take a bit of getting used to.
Personally I love language conventions like this, and think they’re fascinating, so I don’t mind them, but not everyone is a linguistics geek like me haha.

San’s mother changed the order of the court maids presenting to San, because she wanted to make a point to San about getting romantically involved with a court maid, in front of the court maid that he likes, so she could also hear. It was a warning to both.
Of course, history will tell us, that San’s promise to his mother to keep relations within the nobility, will not be kept, nor will Deok Im’s insistence of not becoming a concubine.