Eurgh. I'm sorry this happened. And it's awful when we don't know why.

I was really close with my cousin too, growing up. Then when we were about 20, everything changed. She stopped reaching out and only responded to a few of my messages/ calls. I withdrew and now we don't speak. I would say hi to her at a family event, but that is it.

It's kind of lame and ridiculous of both of our cousins. But like you said, what can you do?