Only in fiction do people look in a way matching their hobbies and actions. In real life, this is indeed how it works: you cannot physically tell the difference between a hero and a mass murderer. I think about this a lot when looking at bad guys like thugs and delinquents in anime, who you can just look at them and say "well of course they're bad, they wouldn't be able to save any kittens from any tree with THAT face" even though that is not how it should work.

Speaking as someone who listens to Rammstein without knowing much German and Dir En Grey barely knowing much Japanese, yeah she might not and probably just enjoyed the music more for the flow, tone, etc. Still she could have also looked up translations and found them interesting (I mean even in songs sung in English I think many English speakers still enjoy songs regardless of some of the lyrics, like the vast majority of people who listen to death metal aren't actually going to do the horrible things described in the lyrics).