Lots and lots of artists start out with a pent up supply of good material inside them, and it all (or nearly all) goes on their first album. There are a handful for whom that supply of good material is just the tip of the iceberg, and the lucky few who can continuously generate a fresh supply. For many others, the supply dries up and they're left casting around for suggestions of what to do.
And, of course, if they had a smashing first album, everyone's expectations are that the second album should be even better. Look up "second album syndrome". As well, all that material going onto the first album or two has a ring of authenticity to it because they wrote it when they were a "starving artist" trying to make it big. Once they get fame and fortune, it distorts their world view quite a bit (for many, not all). People can identify with the songs on your first album about not getting respect or trying to make ends meet, or the guy/girl you have a crush on who won't give you the time of day. Your second album, with songs where either you're trying to remember what it was like back before you were famous - that starts to sound inauthentic - or you're complaining about how your personal chef didn't prepare your favorite dish quite right... fewer people can identify with that.
You get more detached from "the real world", and your material gets weirder. I mean, some make it through just fine, others not so much. Robin Williams' quote, "Cocaine is God’s way of telling you that you make too much money," is funny because it's kinda true. Some of the most brilliant / talented musicians died young (look up "27 Club") - part of their musical energy was driven by their internal turmoil, sometimes that turmoil was exacerbated by becoming super popular overnight (suddenly everyone wants to be with you - that's fun for a while, then you start to wonder if they really like you, or like hanging around with the character you're essentially playing).
I don't think it's a concerted effort by the entertainment industry to get stars involved in the occult, or dark imagery, or whatever (suddenly I have this image of Jon Lovitz as the devil, in SNL's "Iran's Most Wanted", saying, "don't you think you could make this part a little more... blasphemous?"). What I see is a lot of young people who become famous (possibly because they are drawing on the pain from bad events in their past), and then don't cope well with the weird lens that stardom puts on one's view of life, and feel intense pressure to invent something new that's equal to, or better than, the thing that made them famous - and not too different from it, lest fans complain about it not being the thing they like, but not just "part 2" of the first thing because fans will complain that it's the same. And their new material doesn't hold a candle to what brought them fame.
And that website, "Vigilant Citizen", was all about, "no, see, this is a global conspiracy, only we know the truth." Yeah, that is tin-foil hat territory.
She's a teenaged girl. Lots and lots of teenagers go through a goth phase (it's almost more unusual when they don't) - this isn't just something that only happens to musicians (it's a part of rebelling against parents, authority, and society). Though usually there's more black eyeliner and eye shadow involved. Maybe the sleepy / no eye makeup is the new variant of that (it's not something I really keep up on). Fashion does weird things. And you're interpreting intelligence / thinking from facial expression. That seems like just a different variation on the "women should smile all the time" notion. You're just layering different expectations on them. Right after pointing out that the "women should smile all the time" expectation is a problem.
