Sounds like the answer is right there
Why not just run the fan test on your wife's bike to see if her fan performs like yours?
What do you mean by "tested ok"? Not running on the test would indicate it failed the test.
If the fan is struggling to perform as designed, that sounds like a fan that did not test OK and wasn't OK, regardless of the age of the fan. Maybe you can get the manufacturer to warranty the fan, if you feel it failed prematurely.