How to decline belly touches from rude aunt..?

I'm up visiting my parents for the weekend with my husband. My mom is out with her sister today, shopping. I don't care for my aunt. I tried to refuse belly rubs at Thanksgiving and Christmas and she just laughed in my face and told me to "shut up and stand up". I have no issue telling her off, however I don't want to upset my mom so I wanted to go about it in a better way. Any ideas how to handle it..?