I'm not going to be there for my ex
What is your reason for not wanting to support your ex?
My ex is a witch who is impossible to be with.
I know that you don't like being around your ex, but she will view you as cold if you don't help her. Try to be patient with her and support her in her time of need.
Nah, I'm going to stay away from her. She's a terrible person and I don't care how she feels.
While you want to make sure you are there for those you care about, it is fine for you to not be there for your ex if you choose not to. People do not always feel close to their ex, and if you do not have a close relationship anymore, it makes sense why you may not want to provide them assistance.