Why are girls so mean? And why are they so materialistic?

I remember when I was in High school, back when I was a Junior or Senior, and I remember seeing this one girl I really liked in my Anatomy class. I gave her a Poem, (in both English and Spanish) along with some flowers, and well, she just said expressionless like "uhmm thanks". I had some friends tell me that thats how she is, because she comes from a above average/high income family and everything comes easy for her. So me comming from a low income household, I stood pretty much no chance.

So she was pretty spoiled, but not bratty surprisingly, she was very quiet and smiled a lot. but from there on that just taught me that beauty is really just skin deep. and I got so mad after that for falling in love with a girl like that, and that I gave her my original copies of poems and didn't make any copies.