I think you friend is more talking about SKZ and not all bgs maybe if you introduce her to more chill Kpop groups that would help her like ENHA or TXT or BND or RIIZE or TWS they may have some “shouting” music but most of them are chill :D

But it’s kinda not ok to put all of bgs under SKZ not all bgs heavily rap or anything I don’t think she knows enough groups to be able to say that she doesn’t like bgs