Why does my friend act like this?

i had a friend like this and it got to the point where it really narked me off and i was feeling like how you are now, just sit and talk to her telling her how you feel. if she laughs at you and doesn't it take you serious enough then shes obviously not taking your feelings and friendship seriously. shes also jealous by the looks of it when she says shes prettier and deserves better grades. down let her put you down like that, nobody deserves it! :)