Tween book drama

Growing up I had a voracious appetite for reading.  I read books, magazines, the back of cereal boxes, the aspirin bottle.  If there was something in front of me to read I did!  Sierra is the same way.  I've loved watching her grow, learn, and explore through her books.  Unfortunately, her book selections don't always match what I would like for her to read.  Sierra states that she's read all of the books that she wants to read in the juvenile section and now wants to look in the young adult.  Most of the suggestions that I make are quickly dismissed.  She reads REALLY fast!  Much, much faster than me.  So it's impossible to preview everything that she wants to read. 

Everyone knows that books can be very influential.  I vividly remember reading "Sweet Valley High" when I was a teenager and Jessica (I know at least half of you know who I'm talking about!) complained to a friend that her "pores were huge".  I had never really paid attention specifically to the size of my pores, but now that she mentioned it... geez, mine are really big! Look at that - I found something else to obsess about that I didn't even know that I needed to obsess about!  I was telling Sierra yesterday that her hair was so soft and had pretty highlights.  She said "No it doesn't.  It's brown.  Mousy brown.  It's forgettable."  Did you hear my heart break?  I'm almost sure that I've read those exact words somewhere.  I feel certain that she got that notion from something that she read.  So how do I stop this?  How do I keep her from finding more things for her tween brain to become preoccupied with?  I realize that influences come from everywhere for her, but I'd just like for something as wonderful as reading to only have good influences.  Fantasy world?  Maybe.  But I'm open to suggestions!