Friendship problems? help please?

[Dodo]

I have a friend who gets moody quite often. She'll get moody at small things or things that isn't my fault, such as I can't meet her in town because no one can drop me. She'll then be really blunt in messages and usually writes facebook statuses saying how angry she is.

I've had statuses aimed at me before saying she wants to shoot me, saying she hates me and more and overall since I became friends with this group 4 years ago, my self esteem has been picked away at.

However what I find really hard is how they are much meaner to me and I don't get moody or write statuses or send her horrible messages so they don't know how much it hurts. She's agreed to meet me in town, and not turned up, she's invited our other 2 friends in our group to her house and not invited me and tried to hide it, they all go round eachothers houses without me, she gets them nicer birthday/christmas presents, once she got our other friend a £40 one direction ticket..and me a 30p chocolate bar. At school they point out my flaws, and never wait in the places they say they would after lessons. They run off away from me, leaving me on my own. I hate it and that's why I never do any of this stuff to them..because I know how horrible it feels. And then on top ofl all that, thewy copy everything I do, my hair, my clothes-to the exact outfit, my bedroom! Its so annoying and it makes me so upset! Help and advice please?

Sorry its so long!t