What do I do about my oldest friend?

We'v been friends since the first day we started school together 18 years ago. Growing up we where best friends and as kids we where each others shadow, we even told everyone that we where sisters we where so close. Shes an only child, her parents divorced and she never really saw much of her mother, and she lived with her gran mother through her child hood, although her dad wasnt around much he always bought her everything, she always got her own way and anything she wanted, her dad's quit rich. I grew up in the country side with 2 siblings in a lower middle class family, we never really had any money and we certainly didn't get everything we wanted. As adults where both completely different people she has a child, has never worked a day in her life, lives off her dad still, gets the best of everything, big boobs, blonde hair, fancy clothes. Im a student struggling to make ends meet, im a bit alternative in how I dress i love rock music, I buy everything from second hand shops. She hangs out with blonde haired girly girls, most of my friends are guys or girls covered in tattoos and piercings. I always text her or write to her on facebook but she never replies, she'll text me when it suits her and when theres something going on in her life, shes ditched me so many times over the last couple of years. She used to leave me standing out side her house after we'v made plans to meet up only for her to not be there, instead of telling me she didnt want to meet up shed just let me stand around waiting for her. She text me today after a few months of her not replying to my texts, she wants to meet up tomorrow because she has so much to tell me. I just came out of 2 really rough years and im not a push over anymore and I wont be walked on. I love this girl to bits, I know her so long but im fed up of only being contacted on her terms, when it suits her, where both so different. We get on when where together but im fed up of her only bothering with me when it suits her I havnt text her in about 2 months and today she texts me I replied.. and I know I shouldn't have, im just not really sure what to do I dont want to just stop being friends with her but im starting to feel like thats my only option .