How to tell my ex I hate her?

I recently parted ways with my ex. We hadn't been dating, but she has dragged me along saying things like "I don't know what the future holds for us", and in my opinion is BS talk that someone says so that they don't have to commit to you. Long story short, after 3 years of an on and off relationship in which I went above and beyond in helping her with every problem she has had ranging from paying bills, repairing her car, taking care of her child when she couldn't find a baby sitter, and finally taking are of her after a major surgery in which I had to wake up every 2 hours to give meds and empty drainage bulbs, I had found out that she had slept with someone a little over a month prior to me having to take care of her. I immediately lost it and was angry at the fact that I have had to go through so much time, money, and effort for this person, but do not get to enjoy her company at all, while someone else who does nothing for her gets the goods. She claims I am wrong and that I have no business being mad at her. We have since parted ways to a degree but she still calls me to be her shoulder to cry on and I do not want to be Mr. Expendable anymore. Am I wrong for hating her? How do I tell her that I don't have any respect for her and that I despise her so that she understands just how disgusting her actions have been instead of just saying that I'm wrong?