The fact that you have no interest whatsoever in her but still hang out with her will make her automatically have interest in you which means she does not want to be friends with you.. and may actually prefer you to bone her.
If you had interest in her, it would be a lot easier to be just friends with her.
LOL.. Just fall in love with her or something.
She'll see you as harmless and want you to hang around and have harmless fun.
- If she's really hot. That's probally what is happening.
If she's not that hot, then she could just not be use to having guy as just friends and have only ever hung out with girls.