I'm jealous of my best friend?

My best friend Mandy is very attractive and is always the center of attention. I love her and she's not the jealous type. But I am. I get so mad when all the boys ask her out to the skating rink and take a look at me and tell me I cannot go. Mandy never has time for me because of her schedule. She has volleyball, basketball and then her social time at church. I aske her every other weekend if she wants to come over but she can't. I'm sure that she is a little embarred by me, I'm not as pretty as her popular friends and i'm overweight too, so everyone treats me different. I sometimes believe she only talks to me and calls me friend because me looking ugly makes her look prettier. And i've read articles about friends who do that. I'm not usually one to run my problems on someone else and Mandy is my best friend. But sometimes she just makes it hard to be myself. She's so goregous and popualr I change myself to be like her. I'm only 13 and I've learned everything I shouldn't know till I'm 20, i've changed my outfits because if I don't I feel like I don't live up to her expectation, and I used to never wear makeup, but now I plaster it because when i don't no one talks to me and I'm alone again. I'm not sure if this is wrong of me to feel this way. :(