Why does my girl get jealous when I have hot myspace friends?

I just had a really bad argument with my gf about myspace friends. She wants me to delete any hot chick that i dont know from my friend list and I think thats retarded cuz its not like i look at them and whack off to em er somethin, they're just there for show. The friends in question were Mistress Juliya from the fuse show uranium and the female hosts from g4's attack of the show. I can understand mistress Juliya cuz she is very beautiful, but i only friended her cuz im in a metal band and it would be cool if she checked us out and liked our music. As for the other ones, I just like AOTS, I friended all the male hosts from that show too, but I dont have to delete them. The real question is, she feels really strongly about the fact that having them as my ms friends makes her feel less beautiful cuz they're hot and (she thinks) shes not so she doesnt even want me to look at them. Do any other girls feel this way and why?