"Sexify themselves for the sake of relevance" puts a negative spin on it. I don't see any problem with girls being girls, whether that means dressing themselves up for beauty's sake or just having some giggly fun, or being culturally relevant (I rather applaud them for it) or more private or introverted for whatever reason.
Who profits off of it just amounts to who chooses to capitalize on it. There're always people who want to do that, and there's a problem with eventual unequal distribution of resources, and oh well. But even though there are aspects of modern day pop culture that I find disagreeable, girls having more sexual freedom than ever before is not one of them. (I can understand the feeling of it being forced, but it's not "forced out of them". It's just that they're actresses appealing to a certain audience - one that is honestly surprisingly very inclusive. (I mean to pedophiles). Despite the odd escapade with someone behaving "inappropriately" towards a star, which - granted - does suck, the stars themselves do, generally speaking, take a pretty relaxed attitude towards us as a demographic. Why would they not? We're their older brothers' friends (or their friends' older brothers) - often people they look up to or might even have strong friendships with already themselves - who are always cute and kind, showing respect and appreciation for their art and for who they are as people, as human beings. We adore and admire them.
Don't imply pressure where there is none. Pressure - for better or for worse - comes from those close to you; popularity is its own appetite. And there will always be girls who want to be just like the popular girls, and they're cute too.