Then too, there are specific types of critical thinking that are characteristic of different subject matter: ...'thinking like a scientist' or 'thinking like a historian.'" (p.8) "From the cognitive scientist's point of view, the mental activities that are typically called critical thinking are actually a subset of three types of thinking: reasoning, making judgments and decisions, and problem solving.
...[We] think in these ways all the time, but only sometimes in a critical way...
Millbrae, CA: Measured Reasons and The California Academic Press, re-printed with permission by Insight Assessment.
"In layperson's terms, critical thinking consists of seeing both sides of an issue, being open to new evidence that disconfirms your ideas, reasoning dispassionately, demanding that claims be backed by evidence, deducing and inferring conclusions from available facts, solving problems, and so forth.
Maybe she was already developing a cold and that particular day it just happened to manifest itself.
Maybe a sick person sneezed on her in the elevator that morning.
Let's say that these thoughts of skepticism inspired your curiosity.
After all, it wouldn't be fair to simply dismiss all new ideas, either.
Why did your aunt decide to take vitamin C rather than vitamin D, or any other vitamin?
Also, there was never any indication given that there exists a direct link between not taking vitamin C and developing a cold. However, there could be many other variables involved that have nothing to do with vitamin C.