How would you handle this friendship?

I have a friend who I am really considering letting go of for good. I have known her for 5 years, and she is the most negative person I have met. She had a baby later in life by a man she dated for just a few months. She is almost 50 and her baby is almost 3. For 3 years she has told me how unhappy she is and I have told her to get a job. She has every excuse in the world! Her husband only comes home 4 times a year, if that from working out of town. Well, he is not working now, and he is just hanging out in another state. I have told her for months to apply for food stamps or go to a food pantry. She yells and screams into the phone that I have obviosuly forgotten (even if its a tiny thing) since my son is grown and is 24. I have told her several times that I have not forgotten. I struggled too, and had my lights turned off plenty of times, and I know what its like to be hungry. She is the most miserble person I have ever met, and to be honest I don't get any gratification out of being friends with. She really just talks on the phone and if I ever want to get together, she has an excuse. She is really rude, talks over me every phone call, she has a voice like a man so its amplified~ Then, the next time I talk to her, she says, "I really want to say that I'm sorry, its not you, its me". Well, after 100 times, it gets old. All the screaming and venting she does with me, I feel like a punching bag. I am really ready to ditch this friendship but I don't know if I should just quit calling her, or be up front why I don't want to continue our friendship. I have tried to tell her several times that I don't lke talking to her because she is rude and negative and verbally abusive. I told her I feel like since she is so verbally abused by her husband, it has changed her 100%. I have tried to help this woman, but there is no hope. Just pondering a good way to say good riddance!