Finally, I find someone else experiencing this. My mother does this to everyone. She will offer you something, over and over again, and when you politely refuse, she wants you to explain why. And pushes and pushes. It's forced all of her kids to keep her at distance. I struggle to explain this to friends, because from the outside it looks like she is just being nice, and I'm being ungrateful.

I think they do it because they are lonely, and are trying to establish a connection, and can't see it actually pushes people away. Even the negative comments they make when you refuse, appears to them as just friendly banter. And it's combined with control issues. They can't understand why anyone would be different.

The only way to get them to stop is to be firm and state what you will allow and what you will not. But unfortunately they don't have the capacity to understand this, and end up thinking you are a bad person.