Not a true friend being mean, then wants to talk again?

My friend, hazel (pretend name), always talked to me and hanged out with me but then she met some new friends and she wouldnt invite me to hang with them or do group activities in school with them. I talked to her about this (3 times this has happened now the 4th) and she said she would stop but she keeps doing this! I have no friends other than her, sadly because everyone thinks that I think too much of myself even though im really interested in other people! A couple weeks pass by and she then gets a boyfriend and wont stop talking about him which annoys me a lot. Then I introduce her to my cousin and she also non stop talks about him and she tells him more personal things than me and gives him so many gifts! Today, she texted happy birthday to me and said that we should hang out some time. I dont know what to say or do since she was being a bad friend and started ignoring me. I also dont know what to do if she gives me a present tomorrow at school! What should I do or say? I cant put up with her selfishness anymore! Help me!