How is the property deeded?
Are you both on one deed as tenants in common?
If property taxes are left unpaid, the home could eventually be subject to a tax sale or foreclosure.
Assuming that you are tenants in common, then you both have a duty to contribute to the carrying costs of the property.
You may have a few options. You could likely sue your aunt for the unpaid share of the expenses or seek a partition in which the court would order the sale of the building and you could then buy out her interest.
You should consult with a local real estate litigation attorney.
If this answer was helpful, please mark it as helpful or as a best answer. This answer is for general education purposes only. It neither creates an attorney-client relationship nor provides legal guidance or advice. The answer is based on the limited information provided and the answer might be different had additional information been provided. You should consult an attorney.
Attorney Millar's answer is right on-point. Please consult with a real estate/litigation attorney to determine the best options in your circumstances. Good luck to you.
This information is presented as a public service. It should not be construed to be formal legal advice nor considered to be the formation of a lawyer/client relationship.