Sunnydaze, I realize that you have emotional issues over this. But I have to ask how you feel you are making things better? You're making yourself mad over this, and it's not accomplishing anything. Instead of continually getting mad, just don't have anything to do with her.
You gave her a seat to use, and she is the one that decides not to use it. If you feel that strongly about it, talk to the authorities.

But to call her when you're angry? Is that right? If someone called me angry because they don't approve of how I'm raising my kids, I'd be less than hospitable.

Don't hate me for saying this, but you have done all you can do. You have done all you should do. The boy ain't yours.

It's out of your hands.