Also, what I'M interpreting from Na Hee Do and Ko Yu Rim's storylines is how hard it is for them to get what they want.
Na Hee Do is very priviledged in the economic aspect, but lacks a strong support system. Heck, even her mom sometimes chips away the self esteem that she hardly builds.
In the other hand, Ko Yu Rim has a super strong support system. Her parents, her coaches, and even has fans. But lacks the economic dependency. She feels inferior because she doesn't have the latest equipement or newer shoes, and we're told that fencing is a very expensive sport to partake in.
They have struggles, and both are extremely valid, so when Ko Yu Rim trashes Hee Do's efforts, it stings, deeply, and is justified