Please reread the thoughtful answer by Amy J.
Among other smart things she notes:
"I don't think the music itself will hurt her, but you do want to watch her peer groups and activities (or lack thereof) to make sure she doesn't get obsessed with being depressed by glamorizing the downer bands. The same way you should make sure her life stays well balanced in general, she shouldn't be spending ALL her time listening to these bands-UNLESS it's having NO ADVERSE effects on her life. Like she starts quoting these artists all the time for life advice or something... Keeping her busy in other ways will help eliminate the need for a total ban of the music."
She also notes that being into particular music today is not like it was when most of us who post here were teenagers. Now, kids can go online and not just find their favorite band's music (and videos) in a hundred different versions, but they will be directed to similar music via link after link of "if you like band X, listen to band Y too." And they can stream it into their earbuds 24/7, as Amy notes. Just be aware that it's not like your daughter or her friends are just buying an album and putting it on while in their rooms, like it was with us "back in the day." Now they can listen to the music pretty much every minute of every day and see videos on demand instantly. And yes, they listen to it at school too, when they can.
So the exposure is much more intense than when most of us posters were younger. No longer can a parent just charge in and break all the vinyl LPs and that's the end of it; the kid can just borrow a friend's computer to download more of whatever they want. That's why "banning" can become a joke to kids this age.
That's why it's important to be sure your daughter is just too busy with other things (schoolwork, activities she likes, etc.) to have earbuds glued in all the time -- even if she were listening to the purest church music through them, that would be an unbalanced amount of time spent on one thing.
Overall, yes, this is not something to fuss about too much. You will turn it into "forbidden fruit" if you take it away altogether and remember -- forbidden fruit is the sweetest, and she will want to sneak the music if you overreact to it. But use it as a springboard for discussions about why she likes it (she may start out shrugging and saying, "I dunno!").
What would bother me much more than bad language or generally rebellious lyrics would be lyrics that glorify violence against women or lyrics that depict women as nothing but sexual objects. There is a great deal of that today, and if you hear that in her music, talk with her. Don't criticize or ban, because she will get defensive and clam up, but ask her how it makes her feel to hear girls talked about like that.
If your daughter doesn't have any extracurricular activities that she chose and that she enjoys, please be sure she gets at least one good, solid activity that really engages her. Let her choose it. Kids at this age need something that's all their own and gives them positive involvement with adults who aren't mom and dad, and other kids who share their same interest. If she does already have activities, that's great; just encourage those and encourage her to see kids who share those interests.