the way i see it they are not your friends. if color, race, or place of origin is the cause of not being friends well that is just stupid!!!
your friends are racist. every person is different we may have something in common and then we have our differences but that's the beauty of life,it allows us to communicate with other people and interact with them.
if i were in your shoes i would continue hanging out with Lilly, obviously you've tried your best to reach out to your friends but to no success. try to explain that Lilly is no different from anyone else. just because she has different color skin doesn't mean she's like totally different. she's human too with talents and hobbies just like everyone else.
i know it's hard because of all the horrible things people do to you at school, but think about this you're happy when you're with Lilly and your not even doing anything wrong. continue being her friend and maybe just maybe you can introduce Lilly to your buddies gradually...
and if people will see you in school being friends with someone with different skin color, maybe they will copy you and be friends with other people as well.
separating people just because of their race is stupid!
be the better person Jess. Good luck.