Selfish best friend?

I have been best friends with this girl for years. Well we've always been equal in our friendship until she recently lost 20lbs, she is still overweight but hides it well and everyone tells her how skinny she is, well recently she started this like ego trip thinking shes better then everyone else. When i get something new, she instantly wants to borrow it, whether it be lip gloss or sungles, the hardest part is that she will get mad if she doesnt get her way. I dont know how to tell her how i feel because shes the type its her way or no way. The more i've looked back the more i have begin to notice her selfishness. Shes also been hanging out with different people.. and she acts fake.. to everyone, her boyfriend, family, friends, she constantly lies about the dumbest stuff.. what to do what to do???