Answer: Slippery slope
Explanation: Fallacies are errors that undermine an argument by weakening it. They can be illegitimate arguments or irrelevant points and are hard to identify.
There are a lot of Logical Fallacies, but for the sentence above, what best describes Andy's sister's argument is Slippery Slope.
Slippery Slope is when a conclusion is made based on the assumptions that if A happens, the logical sequence of events will be B and the consequence to it will be C. In other words, it's a chain reaction with no evidence that any of the statements are true, like in Andy's sister's argument.
