Hi Dennis,
I have to admit, I chuckled at this. Rammstein fans (and to be honest, all of the metal scene that I've seen), are, in-fact the friendliest and most inclusive bunch of music enthusiasts I've ever been around.
To be perfectly honest, most metal fans are often seen as "outsiders" by the "normal" people, and as such, they are an incredibly friendly group and every metal gig I've been to has had a diverse audience.
In case you need any more convincing, here's one of Rammsteins songs; it's called "Links, Zwo, Drei, Vier". The reason for this is "Links, Zwo, Drei, Vier" is associated with the historic German army (in marching, it means Left, Two, Three, Four)- Rammstein addressed those who accused those of being neo-nazis by writing this song the chorus goes
"They want my heart to be on the right,
But when I look down, it beats to the left."
Rammstein are an awful long way from the right side of the political spectrum, they have said they are liberals. If you need any more proof';
Mein Land - about the dangers of Xenophobia
Amerika - about American culture overtaking local cultures
Auslander - about colonialism and tourism (specifically tourism as exploitation of less wealthy people for certain "pleasures/desires" one might say...)
Deutschland - about how the lead singer has a complex relationship with Germany, he wants to love and hate Germany equally (it makes a big deal of the wrong doing that happened in Germany).
Rammsteins songs generally discuss complex moral questions, but they often hide the meaning behind imagery, as if to show how lots of people are narrow-minded and don't think critically. I'm a bit younger than your daughter, I've been to a fair few gigs (sadly not Rammstein - yet!) with my partner, she's said the metal crowd are by far the friendliest - I certainly don't think you have anything to worry about!