Without getting nasty, at a calm time, tell your mother exactly what you feel using specific language. Every time you talk to her, try to imagine what she might be “hearing” beside your words. Try to hear just her words without her tone of voice or facial expression. What is she saying? What is occurring in her listening of you?
When you know what she hears, if that’s different from what you say, you will know how to address it. It’s even possible that you form a new understanding of each other that either makes you feel differently about the cemetery or gets your mother to stop asking and attacking you over your refusal.