I don't have friends

My friend is acting like I'm her psychologist. I get relationship problems, I get work problems. I try to be supportive. I read every text and really put in the effort to give reasonable encouraging answers. When she gets an answer that she doesn't like she lashes that "That's not how the real world works!" . I know, girl. I'm just trying to be supportive. Meanwhile, my problems, my being miserable... (I only tell her when I reaaaally reaaaally reaaaaaaally can't keep it to myself anymore) get an emoji as a reaction. I don't want to be friends with her anymore. I am lonely, yes, and if she leaves, it'll get even lonelier, but I feel she's sucking a good part of life out of me. Her life is waay better than mine. Yet, I'm the one offering support. Also, I became certain we're not friends when she convinced me to start a project with her. She has just been let go of her job. I was working and still made time to work on the project... .She dropped me halfway through because she went on a trip she had been planning for for weeks and never mentioned and then to prepare for her first day at her new better job. She never apologized, never brought up the project again. I now resent her in a way. I'm still the supportive nice friend because that's the right thing to do, but I feel like I'm not being treated right and it's becoming more and more difficult to bear alongside the misery my own life is giving me. I've always known that she needs friends to replace the family she 'doesn't have' (she has a family but they're not supportive, so she surrounds herself with friends to make up for that) but this is getting too much to handle. I feel guilty because she tells me she appreciates my opinions.... but it's becoming extremely difficult to continue.