All kinds of things could have changed - no way to tell from here what it might be. For example, they may be using new computer software to produce the bills, and it isn't taking the exemption into account. You could first talk with the tax assessor, and also with a tax attorney. Does she have anything on paper stating that she is exempt? You could talk to whoever issued that, too. Best of luck!

Your best bet is to call your county assessor's office. They may even have a web site with a Q&A section. I know here in Colorado, seniors who had lived in their house for at least 10 years received a 50% reduction in property taxes. But then, when the state had a budget shortfall they rescinded it. I was shocked that there wasn't a huge outcry from the seniors and their families, but they just paid it. Then, it was re-instated this year.

Taxes . . . . bleah!!