If you stretch a 12" rule to 15" then it will measure a 15" piece of steel as 12". The rule shows less than the real length - real length 15" is less than the reading on the rule of 12". How can anyone argue the opposite?
I'm pretty sure that in her mind she was thinking about the problem this way: "if you use a stretched ruler to cut a 12 inch piece of string, will the piece of string be too long or too short", but that is not what she asked me.. I'm sure about that.