Tell her to buy you something if she’s uncomfortable lol
On a serious note, are you getting table service or are people going up to the bar and ordering? If table service, I can see why some people might find it awkward, but I don’t think it’s bad to do. If you have to go up to the bar to order, then I don’t even see why she’d think it’s weird.
Hair metal/glam metal is tricky because a lot of it has to do with image, as well as sound, with the evolution stemming from earlier stuff like New York Dolls.
I wouldn’t call Nickelback particularly heavy.
And yeah, grunge is heavy. Nirvana is fairly light for grunge (save some of the stuff on Bleach where you have the Melvins’ drummer and a lot of heavier stuff going on). I wouldn’t call it metal, but I’d say it’s heavy.
Edit: I’ll also say that I think some of it has to do with the time. A lot of what Zeppelin was doing influenced later metal bands. Maybe they weren’t as heavy as Sabbath, but just as influential