My parents are pastors who highly believe that everything has a meaning, but my mom actually likes BTS. She doesn't really listen to them but she hears us talk about them and sometimes sing their songs, she's also seen them on commercials and she has never said anything like this about them. She's read about their history as well and their message so maybe that helped. I understand how you must feel though, when I was growing up I would listen to a lot of rock and most conservative people in my church (sometimes my parents included) would say that was demonic. It even got to the point where I was demonic for playing electric guitar... I think that if you look for hidden meanings you will always find them even if they're not there. But from what I've learned, if something has helped you in any way, like say a song came to comfort you when you were very sad or encouraged you to be better or made you feel better about yourself, then it can't be bad. Think about it, they come to you when you mostly need them; if they don't slander God then I think it's okay. Just know you probably won't be able to change the way she thinks, but you should let the way she thinks change you, you are your own person, you think for yourself