What wrong with my friend? (10points!) pleeaaassee!!!!?

we've known each other forever, our dads have been best friends since their childhood on and off also.....so my friend trys to brag A LOT... for example i took her on myfamily'ss vacation this weekend and whenever we were around the family she would brag at any time possible and when she would brag she would talk very loud so everyone could hear. She brags a lot about the stuff her cousins have, like for instance she will say "yeah we sold out horses, but were getting new ones." and another example is i took her atv'ing a few weeks ago and i let her drive on the trails while everyone was there and one of my moms boyfriends friends asked her if she atv's often because she was good and she replied with "no, i dirt bike." when she maybe dirt bikes once a year... she will also try to look better than me when we go out in public, once she thinks i start to look better than her she will start changing and adding things to her outfit or put on expensive name brand things...i mean she is 16, but she acts immature with the whole bragging thing about stuff thaisn'tnt hers. she also says a lot of bad things about her other friends and talk about how their annoying but the next day she will be hanging out with them, shes a cheerleader and is on dance team bdoesn'tsnt hang out with anyone except me and 2 other people..she also plays world of warcraft and has A LOT of online friends from there that will call her?...but when we go out doesn'tesnt get social, when on the other hand im always talking with people and she kind of sits in the back and irritatedeted..why do you think she acts like this