An update. Again, many thanks for your support.
My cousin sent text message invite a few days ago (BBQ for my aunt's birthday end June). Also thanked me for the card and gave me a progress report. She said lots of things just mounted up. Medication and experts are helping her to evaluate why she did what she did. my offer of an ear was well received.
My mother is still full of angst. I read out the texts to her. She was strangely quiet before starting usual criticism of my aunt. This time I had to agree because aunt had said some things that were factually incorrect. I ended the topic by saying I was well aware of the behaviour within my family and would not become embroiled in it. However, at a suitable juncture I would correct the lies that are circulating.