Am I doing this right?
Are you aware of what exactly you are trying to do?
I feel like I have to make sure I'm not letting my guard down because if I let my guard down I'll get sucked into it again.
This sounds like you are trying to protect yourself and your feelings. And trying to keep from being manipulated back into a relationship that is not working for you. Getting sucked back in is very easy, IMO (it's happened to me so many times). You may want to consider going No Contact. This means no texts, phone calls, emails, talks, visits, spending the night, etc. What No Contact does is ensure that you cannot get sucked back into the sickness. When a person is unwell such as an alcoholic or addict, the way they THINK is unwell too. And usually, talking to them makes me unwell. I can avoid this by not talking to them or letting them in my house.
I also feel like I'm being sort of unfair, as I tend to hold grudges and not forgive, but I also try to remind myself that I've given her 4 years of chances and things have gotten worse, not better.
IMO, holding grudges and refusing to forgive are ways to protect yourself from further damage from another person. I don't know how healthy or unhealthy doing these things are, but it has worked for me in the past. It is a way to reject someone who is hurting you, or who has hurt you. As for feeling like you are being unfair, the way I see the concept of fairness is that it really has no bearing on reality. Fairness is a construct, an idea, a way of thinking, a perception. When in reality, there really is no such thing as fairness or unfairness. Things are simply what they are. People who are unwell, such as alcoholics and addicts, like to use concepts such as fairness and blame to point fingers and to be "right." It is easy to fall for that kind of thinking and reasoning. IMO, you are not being unfair, you are being smart. It is unfortunate that she cannot accept that her behavior is affecting you and that you are not willing to subject yourself to her lies, abuse and mistreatment any longer. But you do not have to go along with her refusal to accept.
I think you are making the wise choice. I hope that you can see how communicating with her is making you doubt and question yourself. Because that is what trying to discuss these kinds of matters with alcoholics and addicts seems to always do, make those of us who try to relate with them doubt ourselves, feel badly, feel guilty all for trying to take care of US. I refuse any longer to feel badly, wrong, unfair, guilty or whatever about doing the right things for me, making the right and healthiest choices for my life. I hope you soon refuse too.
Be good to yourself. Don't listen. Try to find what it is you think you Need from her when you try to communicate with her. Then try to determine whether you really do Need that from another human being. See if you can find it within yourself.
(((hugs)))