What does "mix up" mean? How can I use this?
To get something "mixed up" means to confuse one thing for another, or to make a mistake/have a misunderstanding about something that results in confusion. In this context, the speaker is stating that her group members get confused between the two versions of their song, which has different Korean and English lyrics. Ex: I'm sorry, I got you mixed up with your twin brother. (I confused you for your twin brother.) Ex: There's been a mixup, I sent you the wrong file. (There's been a mistake, I sent you the wrong file.)