Searching for evidence of critical thinking in discourse has roots in a definition of critical thinking put forth by Kuhn (1991),  which places more emphasis on the social nature of discussion and knowledge construction. There is limited research on the role of social experience in critical thinking development, but there is some evidence to suggest it is an important factor. For example, research has shown that 3- to 4-year-old children can discern, to some extent, the differential creditability  and expertise  of individuals. Further evidence for the impact of social experience on the development of critical thinking skills comes from work that found that 6- to 7-year-olds from China have similar levels of skepticism to 10- and 11-year-olds in the United States.  If the development of critical thinking skills was solely due to maturation, it is unlikely we would see such dramatic differences across cultures.
After your investigative reporting, you decide to show your aunt that her beliefs on vitamin C are erroneous by presenting the results of your research. If your aunt is like most people, she will hear this scientifically-valid evidence and still insist that her idea about cold prevention through vitamin C is correct based on her personal experience. Part of critical thinking is demonstrating humility, and many people (in this case, your aunt) have trouble doing this. However, a big part of science is testing ideas and finding out that some ideas were not right. This is good because it allows us to tweak these ideas and test out other ones to get closer to finding out the right way the world works.