Dont know how to handle it

For awhile now i've been considering ending another friendship with one of my friends from high school. She says i'm one of her best friends and she does care when really she doesnt. She doesnt call me, or stop by my apartment anymore, she only now hangs out with other people and she didnt invite me to her christmas party and the crazy thing is, she brought it up to me and didnt feel guilty. If that were me, i would of felt so bad and guilty and ashamed. I may get my chance to get back at her and i dont think its the right way but my feelings werent considered to her. I'm a good friend, i stick up for my friends , i'm always there for my friends but when someone hurts my feelings, they have to know that i'm not going to put on a fake smile and hang out with them. My friend is having a birthday get together. I told her i would be coming and i talked to my mom about it. Lets just say i told her i was going to be there, she'll expect me there but in the end i'm not going to show up. I dont really agree with doing this sort of thing on a birthday but i have to do something. This person has treated me horribly. Im the kind of person who feels bad if i'm hurting someones feelings, that means i care. I may not be handling this but this person has to see what its like what its like to have a friend not be there for them. i am not obligated to go. I dont see why i should. I think after this , i am going to stop communicating with this person, not answer her calls. I had to end a friendship like this before, i cant believe i m gonna have to do it again. I've tried letting things go with this person but its not turning out as i would have hoped.